I dont know how to get the bounty do you have to decap or just kill?

All you have to do is beat the person with a bounty on him, if no one already claimed the bounty, you will instantly receive the TC. Note that you will not get a notification of some sort that you won the bounty, so you have to notice that ny yourself since your TC amount got up.

How to claim the bounty?

It is automatic. You automatically get the tc. Claiming the bounty just means killing the person.