Quick bootstrap: you normally want a "helper" to handle downloading things and running the compile steps (it can all be done manually, and in fact you have to bootstrap yourself the first time that way). I prefer this one, pikaur, due to how well it integrates (looks and feels like pacman) and has a rich featureset: https://aur.archlinux.org/packages/pikaur

After getting that downloaded, compiled and installed then try a sample simple AUR package like "downgrade" - `pikaur -S downgrade` - to get feel for it. https://aur.archlinux.org/packages/downgrade/ It really is kinda that simple, the rest is just learning the basic "how are Arch packages actually made?" which is a good thing to learn in general.