Where was it bought? If it was bought from a dealer, you should get operating lessons with it--how to rethread it, how to tie on the new thread and pull through, how to do different stitches, change/adjust the tension, etc. If it was bought from a discount store (JoAnn's, Walmart, online, etc.) you will have to search out serger classes to learn how to operate it. Do you have a sewing machine repair place that you can take it to? They might be able to give you some tips in case you are doing something wrong. There are also several good books about sergers you could try. Singer Reference Library Sewing with an Overlock http://www.amazon.com/Sewing-Overloc.../dp/0865732485
would be a good one as your serger is a Singer. ABCs of Serging is another good one. http://www.amazon.com/ABCs-Serging-C.../dp/0801981956
The Ultimate Serger Answer Guide is a great book to troubleshoot serger problems http://www.amazon.com/Ultimate-Serge.../dp/0801986451
For example, when threading a serger, make sure that you thread the loopers first and the needles last. Because the needle threads loop around the lower looper, if you thread that looper after the needles when the thread breaks, the lower looper thread will break when you start to stitch again. That's because the lower looper thread has no where to go because it's trapped by the needle threads.
Your serger could be out of time. If that's the case, you need a trip to a sewing machine repair man. First though, check and make sure that your needles are as far up as they go and they are not even. The left needles is usually up higher than the right needle. Do you have the correct needles in the serger? Some serger require special serger needles. And even if it does take universal sewing needles, some brands might not work. My serger has to have Schmetz needles in it; other brands of needles won't form a seam. And make sure that it is threaded correctly. There is usually a color coded threading guide somewhere on the machine, usually inside the door to the loopers. Also make sure that the threads are inside the tension discs. If they are only laying on the outside of the discs instead of between them, there is no tension on the thread, causing large loops of thread in the stitch.
For tension problems, which tension to change depends on what it happening in the stitch. If the needle threads show loops on the back side of the stitch, they are too loose. Tighten them until they are just dots. If the loopers meet on the back side of the stitch, the upper looper could be loose or the lower looper could be too tight. You will need to experiment to decide which is true. Thread the serger with 4 differenct colors of thread (using the color scheme from the threading guide is a good idea). Start with a long strip of fabric. Fold in half the short width and start stitching. Every couple of inches, change one of the tension dials until that thread looks like the picture in the manual. Change fabric strips and go to the next tension dial. By the time you are done with the 4th strip of fabric, your tensions should be correct. For a stitch used as a seam, the looper threads should meet at the edge of the fabric and the needle threads should just show as dots on the back side of the stitch. When you change the stitches, always start with the recommended tension settings and adjust to your fabric.
After you have exhausted all other avenues, you just might have a lemon of a serger. Then your recourse is to take it back to where you bought it and complain. Start with the manager of the store where it was bought and go up the chain of command from there.