Hi Larry,
that might best be asked as a seperate question ie "how do I add pads to an already sequenced song". Might be worth mentioning how the song was created ie easy record, recorded in steptime or from a midifile etc as it may determine whether it's possible to add a pad or not.

Unfortunately I'm not an expert on the sequencer as far as recording songs go. To date I've really only used it for style & pad creation or to play back other members songs.( don't like hearing how bad I probably still sound after all these years (haahaa)
I normally just use them when I play in realtime, though, they can definetly be used when recording a new song from scratch.
( just not shaw how you'd add them afterwards, but I can do some further delving if no one else knows the answer)

best wishes
Rikki