SpringFever, I'm not sure I understand exactly what you mean. You should be able to use that for either a 3 or 4 thread stitch, which would mean you have 2 loopers and 2 needles. Correct?
To use as 3 thread, just omit one of the needles (I believe it's always the outer most left one to leave out for 3 thread, though I always use 4, so can't really remember!)
There should be arrows that show you exactly where each thread goes as you thread the machine. (If you pull the front door down, there should be arrows or a picture in there, too, that shows you how to continue threading). The one farthest right should go from the cone, down into the right tensioner (give the thread a little tug after you get it in the tensioner to make sure the thread is seated properly) and then through the loopers (for that perticular thread) and across the feed bed. Same with the next one in to the left. The 2 farthest left should go from the cone, through the tensioners, around the little thread holder, then down and through each needle and out the back.
Ok, HUGE hint here: When you want to change thread colors, don't UNTHREAD the old color! Snip it way back by the thread cone, then tie on your new thread to the old in a very small knot. Run the machine on some scrap fabric (or nothing, since these babies sew on air and you can do cool things with the thread chains), and the new thread will run right through until you are sewing with it. But, just don't try to make the knot of the new thread go through the eye of the needle, cause, uh, it won't fit! lol. Just snip it when it get to the needle and rethread needle with new color. Voila!
You can't use regular thread on it like the spools you use for a regular machine - they are much too think. Serger thread comes on big cones (cause you go through LOTS) and is much, much thinner than regular spool thread. If you're using regular sewing thread, you may never get the tension right.
Ok, have I confused the heck out of you yet?
Just keep playing with it....you'll get it!