I have a rod in my femur, how can I make my leg stronger?

Long story short, I was hit by a car 11 years ago. My left leg was broken in half and my femur was shattered. A number of surgeries repaired my leg but I decided to keep the rod in my femur because I didn't want to have any more surgeries.My right leg is doing all the work as for balancing, lifting, etc. I want to start working out but have no clue on how to make my left leg stronger. Any feedback would be great.