Well its not easy but you need to do a lot of research there are a ton of different types of programs from 4 to 6 years. The 4 year Graduate entry programs are the most competitive and only accept graduates. You'll have to write the UKCAT or GAMSAT or BMAT or multiple depending on the programs you apply to. You'll also need decent funding or loans as UK schools are expensive.
start with studentroom.co.uk. It is a forum and also an information site and they have articles on how to apply to UK medical schools.