How did the Edomites build their kingdom?

Question

and Where is the exactly location of the edom now?
tnx.

Answer 1

http://en.wikipedia.org/wiki/Edomites

Answer 2

Edom is another name for Jacob's brother Esau-The following info is only a part of a good portion available, I've tried to streamline it so it could be palatable. The Scriptures give a detailed history and full destruction of the ancient city.
***it-1 pp. 678-679 Edom ***

"Seir and Edom. Sometime during Jacob’s 20-year stay in Haran, Esau (Edom) had begun to establish himself in the land of Seir, “the field of Edom.” (Ge 32:3) Thus, even before the death of his father (Ge 35:29), Esau was apparently beginning to fulfill Isaac’s prophetic blessing, directing his attention away from the fertile soils around Hebron and, doubtless, beginning to ‘live by his sword,’ along with the 400 men under his command. (Ge 27:39, 40; 32:6, 8) The record indicates, however, that he still maintained residence or a base camp in the Hebron area, not transferring definitely to the mountainous region of Seir until after his father’s death (1738 B.C.E.). By then his family had grown and his possessions were great.—Ge 36:6-8.

The land of Seir had previously been the domain of Horites (Ge 14:6; 36:20-30), but Esau’s sons dispossessed the Horite sheiks and took over the region. (De 2:12) Thereafter the land became known as the land of Edom, though the older name of Seir still continued to be in use.—Nu 24:18.

Geographic Description. The territory of Edom extended about 160 km (100 mi) from its frontier with Moab in the N, formed by the torrent valley of Zered, down to Elath (Eloth) on the Gulf of `Aqaba in the S. (De 2:1-8, 13, 14; 1Ki 9:26) To the E, the Edomite domain apparently extended out to the edge of the Arabian Desert, while to the W it reached across the Arabah to the Wilderness of Zin and embraced the Negeb highlands region stretching from the SW corner of the Salt Sea on down to Kadesh-barnea. The western portion of Edom therefore came to form the SE boundary of Judah’s territory.—Jos 15:1; compare Nu 34:3.

The true heartland of the Edomite territory, however, evidently lay E of the Arabah, for here the high mountain range, with some points reaching an altitude of 1,700 m (5,600 ft), receives some rainfall. This is because the land W of the Arabah, the Negeb, is considerably lower, allowing the remnants of Mediterranean storm clouds to pass over and reach the higher mountains of Edom, where they release some of their remaining moisture. Thus, archaeological investigations show a string of ancient settlements and fortresses along a narrow tongue of arable land on the highest part of the long mountainous tableland, or plateau, but these run out as one proceeds S toward the Gulf of `Aqaba. Modern Tafileh, about 30 km (19 mi) S of the Dead (Salt) Sea, has large olive groves, though this is due in great measure to the flow of water from eight fine springs, only about 28 cm (11 in.) of rainfall being deposited annually.

Though fertile land was in short supply, this rugged mountainous region held valuable deposits of copper and iron; mining and smelting were carried on around modern Feinan, some 48 km (30 mi) S of the Dead Sea. Evidence can also be seen of the existence of ancient pine forests of considerable size...
No written records have been found from Edomite sources. Secular records of other nations, however, make mention of them. An Egyptian papyrus thought to be of the second millennium B.C.E. refers to Bedouin tribes from Edom entering the Delta region in search of pasturage for their cattle. Pharaohs Merneptah and Ramses III claimed dominion over Edom, as did the Assyrian monarch Adad-nirari III. Sometime after this latter king, Tiglath-pileser III (a contemporary of Ahaz) boasts of receiving tribute from “Kaushmalaku of Edom,” while Esar-haddon, Sennacherib’s successor, lists “Qaushgabri” as an Edomite vassal king.—Ancient Near Eastern Texts, edited by J. Pritchard, 1974, pp. 282, 291.

-The modern day area of Edom, seems to have close proximity of Petra, the unique city. Please note:

*** w57 8/15 p. 489 Strangest City Built by Man ***
"SIXTY miles south of the Dead Sea lie the ruins of what a poet once called the “rose-red city, half as old as time.” It is Petra, called by many an explorer the strangest city built by man. In ancient times this city was virtually impregnable. And no wonder! It lay nestled in an amphitheater of mountains; a long, narrow ravine was the city’s entrance. The inhabitants lived in caves dug out of precipitous rocks and cliffs. They felt secure in their rock-cut homes and boasted of their safety. Even its name, Petra, a Greek word meaning Rock, testified to its security. But despite its vaunted impregnability and despite its blazing glory as a center of caravan trade, the city died; and as a race its people became extinct. Why is it that a city that was so great and secure as Petra today is a desolate wilderness?

The Bible tells us why. The history of its earliest inhabitants, in fact, is found written in the Bible. Mount Seir is one of the names the Bible gives to the land surrounding Petra. Originally this rocky region was occupied by the cave-dwelling Horites. But the descendants of Esau, the son of Isaac, dispossessed the Horites. “So Esau took up dwelling in the mountainous region of Seir. Esau is Edom.” (Gen. 36:8, NW) Thus this rugged region came to be called Edom and its inhabitants Edomites."