How to use the Function Keys in Emacs
The function keys (F1-F12) can be bound to functions in a similar fashion as any other key.
For example, you might set the following three function keys:
(global-set-key [ist:f1] 'mail)
(global-set-key [ist:f2] 'mh-rmail)
(global-set-key [ist:f3] 'discuss)