There’s a common starting point and then a range, and the choice belongs to your provider.
The starting point: wet-to-dry dressings are often used first. Here’s how they work. A wet dressing is applied to the wound. As it dries it absorbs wound material, so when the dressing is removed some of the tissue comes off with it.
Other options include a dressing that contains medicine, and skin substitutes.
Beyond that, your provider may use different kinds of dressings to treat your ulcer. This page won’t recommend a specific product.
Some rules apply whichever dressing is used. Keep the ulcer clean and bandaged. Cleanse the wound daily, using a wound dressing or bandage. Keep the dressing and the skin around it dry, and try not to get healthy tissue around the ulcer too wet from the dressings, because this can soften the healthy tissue and cause more foot problems.
How often to change it is also up to your provider. For a wet-to-dry dressing, your provider will tell you how often you need to change it. You may be able to change your own dressing, family members may be able to help, and a visiting nurse may also help you.
The dressing is not the main event for this wound, and it is worth saying so. Taking pressure off the ulcer is its own part of treatment, and pressure on a healing ulcer for even a few minutes can reverse the healing that happened up to that point. A perfect dressing under a foot that is still bearing weight is not treatment.