Its Got simpler with Android Studio All you need is to first choose
3.based on the type of project and library you used like (ActionBarSherlock) you may prompted special import wizard so go ahead and click next then finish. in this case it was simple one
but sometimes the debug or Run options do not work and a error msg shows like
"this project structure is not gradle based or migrate it to gradle"
something to solve this close the opened eclipse project and reopen same project through the same process as we did before with import project (eclipse adt,gradle,etc)) this time android studio gonna add all necessary gradle files and green debug option will work too. i have did this somehow accidentally but it worked, i just hope it works for you too.