Click the Run button in the toolbar (or press ⌘R) to build & run your project. Click Stop (or press ⌘.) to stop execution.
Click & hold to see the other actions, Test (⌘U), Profile (⌘I), and Analyze (⇧⌘B). Hold down modifier keys ⌥ option, ⇧ shift, and ⌃ control for more variants.
The same actions are available in the Product menu: