I have a slr (A 100).I bought a (VCT-D680RM).what cable conects them together?

Answer 1

The tripod's remote is intended to plug into the ACC (accessory) terminal. But eh, the A100 doesn't have one. The A100 does have a remote socket but this uses a different type of connection.
(Some of Sony's point & shoot cameras do have an ACC terminal. The R1 does, for example.)
Even so, for around $75 the VCT-D680RM is still a pretty good tripod.