I think this is clear...
Right click on the panel to the left of the arrange window (no idea of it's technical name!). And select add FX track. You'll now be able to see it in the mixer. Insert reverb or what ever fx your thinking of. Now, in the channel you want the fx to go onto... just above the fader there's a small downward arrow - select sends. Turn this on and adjust the amount of the fx to go onto that track.
You'll now be able to send as many channels through the sends as you like without having to load a bunch of the same fx.
Before I found this I was wondering how come my CPU levels were through the roof. I now know that it was because I had about 12 reverbs running at once!
Anyway, I hope this is clear and helps