Are you wanting to use the serger to sew a hand knitted sweater together? or do you mean a sweat shirt knit or other knit fabric. If it is the first option, I'd say don't bother, as you can't do it with the blades working because it will cut your knitting and the wool will unravel in the seams.
If it is the second option then I would start with the following settings.
Four thread stitch, so both needles and the upper and lower loopers threaded. Set tension on all four dials to 5, stitch length to between 2 and 3, and differential on zero. Move the cutting blade over to the right for a wider seam. Now test stitch on some fabric scraps double layer and see what the seam is looking like.
Now you want to adjust a couple of things: firstly width of the seam. Is it the size you want? If you'd like it a little narrower, then adjust the cutting blade back a little to the left to narrow the seam slightly - just depends on the fabric weight. For example if it is a loose open weave like boucle you would want a wide seam to make sure it holds the fibres fully.
Now you can adjust the upper and lower loopers to get the thread wrapping around the edge looking nice. Look at the seam and the fabric inside it. Is it tunnelling and pulling up the fabric? if so, release tension on both loopers a half number to put more thread into the seam. Test stitch again and see if the loopers are meeting nicely on the cut edge of the fabric. Upper and lower looper threads should be meeting right on the cut edge so if this isn't happening and one showing on the other side, then tighten the looser one by half a number and test again.
If the threads are hanging off the edge then you have the choice of moving the blade to the right to cut less fabric off, or tightening up the looper tensions to pull in the thread.
That's it, hope this helps you to master your serger.
If you'd like some images and further explanations of other stitching you can do with your overlocker, then Debbie Coswell has some great information on line at www.sewing.about.com
, just search "overlocker" to find the specific pages.