Typically the missile is steered with a joystick, and its path is observed through a periscope-type telescopic sight.
MCLOS requires considerable training and practice to master, since even a minor disruption in the gunner's concentration would likely cause a miss.
These guidance systems have marginal accuracy on tank-sized targets, even with perfect line-of-sight by the gunner, due to erratic flight paths requiring timely manual corrections.
MCLOS guidance today has mostly been replaced by the easier-to-use semi-automatic command to line of sight (SACLOS), which allows the gunner to merely track the target with an optical sight (which guides the missile), rather than being forced to both visually track the target and fly the missile manually.
Actual figures from combat operations suggest that it is much lower than SACLOS guided missiles.