You'll need either a mixer to plug the mikes into. Run one line out from the mixer to the line in of the PC to use reaper or whatever to record. Depending on the type and number of mikes and amount of money you want to spend here are some to dream about:
http://pro-audio.musiciansfriend.com/mixersYou can start small with 2 or 4 mike mixers being quite cheap and always use them for something else later or resell them when and if you step up. A 4 mike mixer with a mike on the snare, bass and two overheads can give great recorded sound actually or even two overheads only is not too bad.
Or you could record each mike on a different track but that gets expensive:
http://www.m-audio.com/index.php?do=products.family&ID=USBinterfaces