You place your bet at the vBetting shop. You can access that from http://www.menstennisforums.com/vbookie.php?
You obviously fall to vCash: $0, and when a new match is posted Amanda will give you $25.
There is a tennis tips thread in the Gamblers Lounge. To make it easy, they create one thread per day discussing the day's matchups.
Cheers and best of luck, bro!