Once your executable is ready after the build, you can execute it by clicking on the Execute button in the extended toolbar, choosing the menu item Build->Execute, or pressing F3.
Unlike the build stage, execution doesn't check for dependencies (at least for the time being). In other words, it does not check if the executable is up-to-date before it executes the program. So, you must take care of that yourself.
If you want to pass any arguments to your program, choose Build->Set Program params …, enter the arguments in the dialog that appears (shown below) and click OK. You can also specify whether the program should be run in a terminal or not.