Take some large scraps of fabric and start by just turning the wheel manually to make sure you are getting a stitch, the threads are not knotting up as you go, and just to see how the blade works, etc. Once the fabric is in there a ways, slightly depress the pedal for just a few seconds at a time. Once you are a little more confident, keep the foot down longer and focus on feeding your fabric. You will get there.
Don't worry too much about the different stitches yet. Choose one that suits how your machine is currently threaded. Once you can sew with it, practice adjusting tensions one tension at a time to see what happens to the stitch. Practice one thing at a time (such as tension, stitch length, cutting width) until you are comfortable with all of them. Only then would you want to change to a different stitch type and start all over.
Don't worry; you will get there!
Check your area for a serger class. Often community education will offer one, or a sewing machine dealership might offer a class in learning how to use your serger. Fabric shops that offer classes are another good source to check out.