First press the [INPUT PATCH] button.
Select either the Ch1-48 or Ch49-56 pages at the bottom of the screen to call up the channel that you would like to route input to in the display.
For an example on how the routing works, lets say that you want to route input from your Option Slot channel 3 into input channel 3, which is normally set to AD3, which is analog input # 3.
To achieve this, select the Ch1-48 page and then select channel 3, then use the data wheel to change the selection from AD3 to S1-3, press [enter] to make the setting set. You have now routed signal from option slot input 3 to channel 3 on the board.
Reference pg. 52 in the manual.