There are a ton of different approaches you can take.
These are just loose concepts rather than specific instructions so bear that in mind:
You could make 3 copies of the same individual track, then pan the 1st 100% left, pan the 2nd 75% left and the 3rd 50% left (those are random/rough numbers, so don't take them as Gospel). If there are any phase issues, you could put a very slight delay on 2 out of the 3.
Additionally, presuming each of your tracks are currently in stereo, you could also experiment with summing the track you intend to pan into mono, and then playing with the copy/paste/pan method above.
There are also VST plugins out there that will let you alter the stereo field of a given track. I'm only personally familiar with the S-1 Imager from the Waves bundles (which cost thousands of dollars) but I am confident there are a bunch of free ones out there.
There are other options, too. As mentioned before me, there are plugins that will 'widen', and do all sorts of other crazy things. I guess I just prefer doing what they do the hard way.