Your doctor has recommended that you use a walker. A walker is useful when you cannot put your full weight on one leg or foot, or when your balance is a problem. You should be sure your walker is adjusted to the proper height, and use it whenever you walk. For non-weight bearing, hold your injured foot off the floor, and lift or roll the walker forward about one foot, "plant" all 4 legs of the walker, and support your weight on your hands. Then move your good foot forward to the center of the walker, and repeat.
If you can bear partial weight or if you are using the walker to help with your balance, start in the center of the walker, lift or roll it about one foot forward, and "plant" the 4 legs on the floor. Step forward, using the hand support to help keep your balance. If you are post-op or have an injury to your extremity, step forward with that leg first, then bring your good leg forward to the center of the walker, and repeat.