Unlike the AVR Studio 4 to build your project, without starting debugging, you should press F7.
If you need to rebuild your project after a change to the source files, press Ctrl+Alt+F7.
To Start debugging - press F5.
To open the Debugging Interface without running directly, press the Debug→Start Debugging and Break menu button, or press F11.
To start a line-by-line debugging press F10, to start an instruction by instruction debugging session - press F11.
To run your project without debugging, press the Debug→Start Without Debugging menu button.