how to press F1 with the Mac pro?

Morning Mennito,

This will help you learn how to change the behavior of the function keys on your Mac.

Mac OS X: How to change the behavior of function keys

http://support.apple.com/kb/HT3399?viewlocale=en_US

Mac OS X 10.6: Using keyboard function keys

http://support.apple.com/kb/PH7052

Have a nice day,

Mario

Also something to consider you have listed your product as "MacBook Pro" but asked about Mac Pro. The Mac Pro is a much different product than the MacBook Pro. Given, the answer to your question would be the same regarding both the Mac Pro and the MacBook Pro. However, for clairty you should always list your product correctly to ensure you get the best answer.