How to treat pressure "bed sores"?

Remove risk factors. Bed sores or pressure ulcers/wounds are caused by ischemia (lack of blood flow). Pay attention to how often you move or shift in place even in a comfortable chair. That's to avoid excess pressure & lack of flow in key areas such as bony prominences. Best way to treat is therefore to remove risk factor, eg immobility: change position frequently. Clean wound (enzymatic or mechanically). Eat protein.
Pressure sores. Pressure sores are due to pressure which needs to be relieved in order to prevent further damage to the area in question. Seek assistance for other treatments from a clinician that is familar with this type of skin injury.