The process for me was a bit different than it may be for others because I was first interviewed by the client that I would be working for then when they offered me the opportunity to work for them, with agency approval, then I was given the agency to contact to submit my application to. However, I still had to meet all the agencies testing standards and requirements before I could be gainfully employed to work for the client. Your experience may be different if you are going to the agency seeking clients though.