If you have copied the loop to track it should be a case of right clicking the loop you want to copy and then right click paste within it's sequencer track, note you can't cut and paste whilst the song is playing. If you put the notes in youself you can colour co-ordinate your loops using the pen tool at the top of the sequencer. This makes cutting and pasteing allot easier. Make sure that you have the "snap" on and set to 1 bar or half a bar etc.