I just checked the unreal site, and it's straightforward - click on the big Download button presented in the center of the page, takes you here
https://www.unrealengine.com/en-US/download
and the page states What does it cost? It's free to use. And mentions the 5% royalty if you make a lot of money somehow, scroll down and there are instructions to download the epic games launcher which is where you install the unreal engine (and also where you get epic games).
But if what you want is free, I suggest you try godot, which is open source and thus really free.