To apply for supported housing in the UK for people over 55, you can contact your local authority or a housing association:
Local authority
Many local authorities use a choice-based lettings scheme, where available properties are advertised on their website. You can register using their housing application form, and they will assess your needs, such as your current living situation and any medical or social requirements.
Housing association
Sheltered housing for rent is usually provided by housing associations, who work with the council for applications and to fill vacancies. You can register with a housing association’s service to apply for sheltered housing.