Sekhar, Yes, you need to know at least one J2EE concept before effectively using WAS. It's overwhelming to do both concurrently. Good starting points are Servlets (front end) and EJB (back end). What version of WAS are you using? That version will determine what version of J2EE you can use. And J2EE has changed enought that you'll get different book recommendations for earlier vs later versions.
Sekhar, That's good. Knowing about Servlets gives you enough knowledge to understand the server. I suggest looking at the redbook corresponding to the version of WebSphere you are using and work through deploying a servlet.
For EJB, you need to decide if you want to learn EJB 2.1 (WebSphere 6) or EJB 3.0 (WebSphere 7.5 beta) as they are quite different. I think going with EJB 3.0 is better at this point. For 3.0, I recommend "EJB 3.0 in Action".