Yep, like he said, CTRL-T will pop in new tracks. But you'll want to make sure your audio device is selected in preferences. Then, press the R button (to arm the track) on the track And for a track, right-click to see options, like which input to listen to. After you've tracked a signal, create a new track, un-arm the first track, and arm the second one. Now you'll hear the first track, but record your new signal into the second track. Keep this going, and soon you'll have a whole bunch of things going on =). Welcome to Reaper, btw.