I am integrating twitter in my android app. I am able to authorize the app for the user. Now, I am looking for the API which gives me logged users information like first nam
There are a few tutorials here that can help you get an app running with twitter..
if you just need to retrieve info for a specific user, you can look here (includes source code):
Basic Adroid Twitter Integration
If you want to interact with twitter (e.g. post updates etc) then you will need to setup OAuth connection:
Android and Twitter integratin using OAuth