ELI5: You read the fine wiki and follow the instructions step by step. You may find the TailsJoin Installation Guide clearer for the first steps, although it doesn't cover the yield generator.

As far as earnings go, the current situation suggests that you'll earn roughly the same amount as you'll spend on transaction fees. If you provide liquidity perpetually without ever initiating transactions yourself, you'll be lucky to net a single percent gain after a year.

Disclaimer: this back-of-the-envelope calculation was performed on a virtual envelope using invisible ink. I suggest you run a yield generator for a couple weeks and extrapolate from your own experience.