Using a wall or chair for support, lift the heels by raising up onto the toes with both feet then lower back down. Repeat this movement in a slow and controlled manner for 8-10 repetitions. Repeat for 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.
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.
You can also progress to working on single leg calf raises.