It really depends on what effect you want. As already suggested you can adjust that way but that only gets you the same level and same sounds, but just from both speakers.

If you're doing stereo you could copy the track, then set one to left, the other to right and adjust panning on each to control which speaker gets a louder signal. Better, if you're using 5-1 adjust the sliders.

While you can't really make it sound like real stereo you can munulipate each track differently with some of th FX audio filters to get some interesting results that would add a little life into it anyhow.