You should read the "How to add girls" thread Anthaeus suggested above. It covers all this. But for each girl, you need to make sure that:
1.) Your .girlsx file has the girl's name in it. In your Resources>Characters directory, you have a folder with the exact same name, spelled and spaced the same way exactly.
2.) In that folder you have all her pictures. The pictures must be named in the standard way. Profile pictures named "profileXX.jpg" where XX is the number of the picture. Anal pictures are "analXX.jpg", beastiality are "beastXX.jpg", lesbian are "lesXX.jpg" and so on.