do i plug the amp in or the actual guitar
Try both and see what sounds best (only use the direct output from the bass amp, not the speaker out...your friends should know where the direct out is if they've ever played live). If you have a DI box, try that as well.
Also, if you're recording more than one note at a time you can get some uneven levels w/ bass guitar, so you might want to try putting a compressor in line after the bass/amp/DI box if you have one. You could try a little bit of EQ too. Whether or not you have access to a compressor and/or EQ, try recording w/o any signal processing first. Hopefully your bass-playing friends are willing to be patient and let you experiment.
Good luck.