1 - Click on Profiles and add your character(s). Resistances are optional.
2 - Then, to sign up for a raid you just click on the raid name in the raid tab.

The following is the order you need to follow to sign up for the first time, and later times:
1 - Go to blackfangs.org/phpraid
2 - Click on "Register" on the left. This will bring you to the alternate forums. If you've already registered for the alternate forums - you can skip this step. When registering you MUST use the invitation code: 9f38c6ac. This is to prevent the spambots from signing up.
3 - Login with your alternate forums username/password (If you login on the alternate forums, you will automatically be logged in on the phpRaid site - and vice/versa).