james hardy,
Greetings. You'll need to purchase either Milkshape, or FragMOTION to do this easily...personally, I've had great success with FragMOTION.
There is a FPSC biped skeleton floating around these boards. You'll need that, if you wish to give a creation of yours the FPSC stock animations.
If you want to import your own model with unique animations, you'll need to export it to .x format, and create a custom .fpe file for the entity.
It can be done. Patience and practice! Do a search for the Milkshape FPSC Biped, and that'll get you started on your way.
Thanks,
Seth Black
Own It, Or Get Owned...