Ducati Monster 796 Workshop Manual page 76

Maintenance operations
Checking rear brake pad wear
Check through the slot between the two half callipers that there is at least 1 mm of friction material on the pads.
Important
If either of the pads is worn, both pads must be renewed as a set.
Change the brake pads as follows.
Remove the snap ring (7) (on the inner side of the calliper) from the pad retaining pin. Force the brake pads apart to
push the calliper pistons into their housings. Withdraw the brake pad retaining pin (8) and pull it out.
Remove the clip (9) from between the two calliper halves. Remove the worn pads.
Insert the new pads and clip (9). Slide in the pad retaining pin (8) and secure it in position with the snap ring (7).
Note
Change pads that have a shiny or "vitrified" appearance.
Operate the brake pedal repeatedly so that the pads are bedded in against the disc by the force of the brake fluid.
Check that the brake fluid level in the tank is between the MIN and MAX marks. If this is not the case, unscrew the tank
cap and top it up.