I own an SP-404 and a Microkorg. I know this is a very noob question but I don't care, I just want to move on with making beats since I haven't made many yet. How can I combine both instruments and loop them together in beats? I want to add drums from the SP-404 over them too and smoothly loop all of it together.

you have to either sample individual notes into the sp and play your notes out off the 404, or you can play a live performance over your drums by turning the ext. source on and recording into a tape deck or any sort of recorder. the 404 cannot re-sample with the ext. source on unfortunately.