In Eclipse you just clicked the new button and select the android activity to add new activity. But Android Studio is a bit diferent; I couldn\'t find out how to add new act
In Android Studio, go to app -> src -> main -> java -> com.example.username.projectname
Right click on com.example.username.projectname -> Activity -> ActivityType
Fill in the details of the New Android Activity and click Finish.
Viola! new activity added to the existing project.