If the client is interested in hiring you, he'll reply to your application.
Then you can discuss the details of the project and agree on the price. Upon agreement, client will hire you and prepay the funds for the project.
*Do not start any serious work before funds are prepaid.*
*Do not accept "half now, half after completion" payment*
First you need to protect yourself to get paid after finishing the project. Client's funds are secured by CGT. You'll get paid only after you send to client what he asked and what you agreed for. If the client "runs away" after he gets the final files, you can always ask CGT support to review the project and to release funds in your favor. This is why it's important that the funds are prepaid and secured by CGT.
I just checked my profile and I see that I made round 50 projects in last two and a half years. So far, I wasn't scammed. I apply to projetcs that I belive I'm capable of doing. Also, I don't apply to projects If I see thet I might have communication problem or the price is too low.
Keep in mind that many designers apply to same project and clients often choose the offer with smallest price. It may take some time and many applications to get hired.