If you are just starting out and want to know more there is a good introduction on the R.S.G.B (Radio Society of Great Britain site).
To get an Amateur Radio licence you need to progress through the 3 levels of licence. Study for the first level is straightforward, and may be accomplished in a weekend.
There are excellent online courses available such as those provided by Billy GM6DX https://gm6dx.thinkific.com/
You can also take a look at https://www.essexham.co.uk/train/foundation-online/ this has further links to YouTube videos and a raft of training materials.
We can also recommend the books produced by the R.S.G.B see the cover images below. Click on image for details
These are available even if you are not yet a member of the R.S.G.B and are just starting out.
The Exam Secrets book from the R.S.G.B is also highly recommended.
Above all there is help from S.A.R.G members who will be only too willing to help guide you through the process, so please do come along to our monthly meetings