Using a wall or chair for support, lift one foot off the floor.
With the working leg, raise the heel off the floor and up onto the toes. Then lower back down in a slow and controlled manner.
Repeat for 8-10 repetitions. Complete 2-3 sets. Over time build up the repetitions to 3 sets of 20.
If this is too difficult then reduce the amount of repetitions and/ or sets. The other option is to change over to double leg calf raises.
If this is too easy then start add some load either by using a barbell or if at home, use a rucksack and add some books or tinned food to add weight.