An occupational therapist helps those who are disabled, injured etc learn to walk again, develop, improve their walking, moving, etc.
The occupational therapist uses therapeutic ways of treating and helping those people with those injuries, etc recover and learn to cope and walk again and hopefully regain their normal activities.
For example if you were in a car accident and then lost a leg or were unable to walk on your own at first then the occupational therapist would then help you learn to walk again.
Or the occupational therapist would help you learn to walk on say a prosthetic leg etc.
They basically help you learn to do your normal activities when you're disabled, injured etc.
Or if you had a stroke the occupational therapist would help you learn to walk and do your other activities.