Hey dude, for what you've said those "smooth curves" that the mesh is deforming to could be because of the skin weights haven't been painted properly and so the amount each joint is effecting the vertices on the mesh is sort of spread out through them all too evenly, giving you a completely different set of stress points than you actually want. There are tutorials about skin weighting all over the net, but i'd recommend one that involves using the component editor to adjust which vertices are weighted to which joints since this really helps you out before you start painting sometimes (especially for thinly spread weights as your problem may well be).
As for the keying, you dont need to go into the dropdown menu and do it for FBIK specifically, an FBIK rig should have a load of effectors on it (little pre-made nurbs curves and spheres attached to the skeleton), and by moving these the skeleton reacts. So, if you move these shapes and key them just like you would any object then your skeleton will follow and you'll have an animated skeleton!
Hope that helps man, good luck!
Tom