My arrow rest is adjustable but I don't know where it's supposed to beset at.After I started shooting it I noticed it was loose and it rotates up and down.By the way it's the fork type rest.What is the correct name for this restso i'll know for future questions and how do I set it?
Thanks,
JE

It needs to be set so that when your arrow is shot it comes off the bow perfectly. The only way to find out is to tune the bow. Here is a link to explain what I mean. What you have is commonly called a prong rest, or TM hunter sytle.
http://www.broadheadtests.com/TUNING.html

5shot's link should point you in the right direction. It sounds like the lockdown bolt that connects the rest to your bow became loose. If you don't know how to properly tune a bow and 5shot's site looks like greek to you then I would suggest visiting the local pro shop.

Hope, either way, you get it fixed.