How do I reconfigure the function of one of my Mentor MP drive's digital inputs?

First use 4.21 in the Mentor MP user guide to determine which digital input (input 1, input 2, etc.) you are looking to reprogram.  (Note that some digital IO can be configured as Inputs or Outputs via parameter 8.31, 8.32, or 8.33).

Next, identify the destination pointer parameter for your desired terminal (i.e. for digital input 1 it is parameter 8.21).  If you are looking at digital I/O 1, 2, or 3 you also need to ensure that the output select is OFF to make the terminal in question an input.  Once that is done navigate to destination pointer parameter corresponding to your input and edit the value to your desired parameter.  Press the red reset button on the keypad to make the change take effect.

Perform a parameter save.   

How do I save the parameters to my Mentor MP drive?

Where can I find user guides (basic and advanced) for the Mentor MP, Quantum MP, or FXMP25?