Charles,
I do not actually know this particular keyboard, but I would assume that the principle is the same.
So to paraphraze your question, you have multiple sequencers and you want to play all of these sequences at the same time. You want to assign a channel number per track. So I assume XP-80 is 32 multitimberal meaning it can play 32 distinct channels at the same time. In order for it to do that, it needs two midi inputs because each midi port handles 16 channels only. After worrying about midi connections (most likely you will be needing a midi patchbay to do all of that, and I assume you already know how to connect all of this), in my keyboard, I would go in song mode and select midi configuration. For each track, I would select the midi channel and select the midi input. Then you need to worry about clocking and since you are playing for multiple sequencers, it is vital you have once clock source and you handle this through a smart batchbay. So it seems to me what would make since is that you set XP-80 to internal clock and export clock to all other devices and thus you need to worry again about the midi out ports in XP80 and set all other squencers to external.
However, it maybe your problem is as simple as playing only ONE sequencer at a time. In this case, this should be a piece of cake. Take care.