Literary theory is complicated and large, but there are a lot of good resources for someone who is just starting out.
These works provide good introductions to theoretical concepts, and citations for further reading.
These handbooks can help you to better understand theoretical concepts and their histories.
Critical Terms for Literary Study by 
The Encyclopedia of Literary and Cultural Theory by 
The Johns Hopkins Guide to Literary Theory and Criticism by 
Literary Theory by 
Literary Theory by To understand the critical conversation that is already taking place, you may wish to consult:
