Upvote:1
Your question is answered unambiguously with a simple Google search and the answer directly from UK.GOV
How long it will take?
The earliest you can apply is 3 months before you travel. Example: You can apply from 16 March if you plan to travel on 15 June.
Pay which fees? If you mean school fees, then there is no need in paying fees before the visa is issued. Many people lose nonrefundable fees that way.