Plate mounting steps are as follows:
The inking and dampening rollers will need to be locked off to prevent them from contacting the plate during mounting.

The gripper edge of the plate is then inserted into the leading clamp. Holding the plate and will keep tension on the plate while it rolls around the plate cylinder. The trailing clamps at this point would be tightened.

Pic 1.07
Above is a movie of mounting a plate on the plate cylinder.

Pic 1.08
Here, the plate is being secured to the plate cylinder.