Its quite easy - here's a link a google search (I googled for you!) https://www.google.com/search?q=mining+guide+ethereum&oq=mining+guide+ethereum&aqs=chrome..69i57.2531j0j7&sourceid=chrome&ie=UTF-8#safe=off&q=mining+rig+ether+guide

I'd read through a few of those pages, but I'll give you the TLDR version:

Have a working computer with 1 or more modern GPU (GTX 1050-80, rx470-580, etc)

Download a miner (I'd recommend Claymore's dual ethereum miner (this can also be googled))

Get an ethereum wallet (there are many ways to do this ranging from complicated to easy).

Go to your config file in the claymore folder and direct it at a pool. (google "eth nanopool" and go to their "help" part, they should provide an address).

Start mining.

When you are ready - start messing with your cards with MSI afterburner, and consider bios modding amd's RX cards.