See A-Z of rehabilitation exercises
In case you cannot see the video, here is a still sequence -
Stand in a relaxed position in front of a low step.
Step up onto the step with your bad leg, and then step up with the good leg...
...to stand with both legs on the step.
Step down again starting with the bad leg, and follow with the good leg to stand back on the ground again.
Start the regime with 10 reps. If it is too easy you can use higher steps or small ankle weights.