Double-click the file that says "Robot Arena 2.exe" and it should start the game. If you don't have recognized extensions set to visible than you might just see a file called "Robot Arena 2" which is exactly the same.
If you don't want to open up the Robot Arena folder every time, you can create a shortcut on your desktop by right-clicking the "Robot Arena 2" file, hovering over "Send to", and left-click "Desktop (create shortcut)" in the submenu that appears.
I'd recommend creating an account and posting questions like this in the General Support board in the future. You'll get a much faster response and it will allow others to benefit from your questions (only staff and guests can see this section).
