If you mean the dual-function 'F' keys, try pressing & holding the 'Fn' key on the bottom row, then press the appropriate 'F' key for the function you wish to apply or enable (the 'F' keys are not designed to type anything).
If you mean the dual-function 'F' keys, try pressing & holding the 'Fn' key on the bottom row, then press the appropriate 'F' key for the function you wish to apply or enable (the 'F' keys are not designed to type anything).