there are a few ways to earn then. You have already earned $0.50, when you were went from hack to amateur. Another $1.00 when you achieve pro status and yet another $2.00 when you make master.
You can also earn credits if you place in the top 70 or top 30 of ready gos tournaments.
Or you can do some of these offers...
http://www.wgt.com/user/offers.aspx