Set up a charity https://www.gov.uk/setting-up-charity/set-up-a-charity
How to set up a charity (CC21a) https://www.gov.uk/guidance/how-to-set-up-a-charity-cc21a
What makes a charity (CC4) https://www.gov.uk/government/publications/what-makes-a-charity-cc4/what-makes-a-charity-cc4#part-2-about-charitable-purposes