How do I get my fiance to the UK?

I, 19 F, a UK citizen, plan to marry my American fiance, 19 F, and have him come to move to the UK.

I'm trying to figure out all the legalities of it but I'm incredibly confused on all the visas.

How would he actually be able to move here after we get married?

We plan to save up for several years (2-3+ years) while I'm in university but we want to try figure out the legal process so we actually have a price goal to aim towards.