Go to your supervisor and tell them you want to quit. They will probably ask you why and go ahead and tell them whatever the reason may be. Tell them you will give them two week notice before you actually leave/quit so they can find a replacement for you. At the end of two weeks your done and can do whatever you want to do next.
Always leave with class and never burn bridges. For example, thanks mr smith for the opportunity to work here. I'm pursuing other options. I hope you'll accept my 2 week notice. It is not my desire to leave you in a bind.