https://tsplines.com/resources/uvtut.html

Run through this tutorial, ignore all his talk about T-splines...its really hard to explain UV unwrapping and PS painting in a thread...but that tutorial is a start. There are lots of similar ones out there for ya too...just search "maya tutorial, UV"

edit: going to find a better tutorial

Here is another one...again not so good:

https://www.tutorialized.com/tutorial...er-UV-Map/4069


And another:

https://www.cheuk-lee.com/tutorial%20...UVTutorial.htm

Eh, and another:

https://www.andrew-whitehurst.net/eyeTut.html

Just try them all...