figured it out. the instructions do not make this part known at all.
My directory is:
mpfenv
---bin
---include
---lib
---project (this is the Godot project folder I created)
-------------addons
-------------config
-------------data
-------------logs
-------------modes
-------------slides
I had updated the config.yaml file located in project----config, and I created my attract slide and attract.yaml in both the modes folder and the slides folder because I couldn't figure out the instructions. This didn't work.
In order to get my attract screen to show, I had to update the attract.yaml file buried under mpfenv----lib----python3.11----site-packages----mpf-----modes----attract-----config----attract.yaml to add the "slide_player: mode_attract_started: attract" code.
I NEVER would have figured this out based on the instructions - just got lucky poking through every folder and subfolder.