what were the steps taken by the US to gain and control the Panama Canal?

Answer 1

Below is a very good source for you. The U.S. government engineered a revolution in Panama separating it from Columbia so concessions could be made for the U.S. canal zone.
Walter Reed was dead by the end of 1902. It was mainly Dr. Gorgas who defeated yellow fever in Panama by drainage of standing water and insecticides by the ton to wipe out the mosquitoes that carried the disease.
Here's an excerpt of the material in the link below :
In 1902, the United States reached an agreement to buy rights to the French canal property and equipment for a sum not to exceed $40 million. The U.S. then began negotiating a Panama treaty with Colombia.
When Colombia grew reticent in its negotiations, Roosevelt and Panamanian business interests collaborated on a revolution. The battle for Panama lasted only a few hours. Colombian soldiers in Colón were bribed $50 each to lay down their arms; the U.S.S. Nashville cruised off the Panamanian coast in a show of support. On November 3, 1903, the nation of Panama was born.
The U.S quickly assumed parental interest. Americans had written the Panamanian Constitution in advance. A payment of $10,000,000 secured a canal zone and rights to build. Bunau-Varilla, installed as Panamanian minister to the U.S., signed a treaty favorable to American interests.

Answer 2

The French tried to build the canal manually, with pick and shovel, but gave up when too many workers died of yellow fever. The US then gave it a go with powered equipment (steam shovels) and better medical care- until Walter Reed (American physician) developed the vaccine.

So, the US gained control by BUILDING IT in the first place.