There are several guides to installing in our Tutorials & Guides category.
https://ubuntu-mate.community/c/tips-tricks-and-tutorials/tutorials-and-guides/
I like this one - ubuntu-beginners-guide-complete-how-to-install-and-run-first-update
Lots of reading there. I'd read this, take a rest and come back and read again. Good luck CraigW.
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