go to My FA, then scroll down to Account Management, then click Upload/Change Avatar. You'll have to pick something that's 100x100 pixels, if I'm not mistaken? something teeny tiny, that's for sure >w< it can be a gif, but whatever you've got's just gotta fit, and once there, you can change avatars there no problem :3

Ah yeah I found it, sadly do not have anything that small. Thank you though :3

np, hopefully you can edit up something >w<
Otherwise, there are plenty of artists who take commish's on here that make avatars :)