Hopefully there are topics you care about and provide you enough basic information to go on, if now however feel free to join the discord channel and chat some more about it in there.
There are also a number of examples within the project folders you can just look over or check out and run yourself.
This project contains lots of running examples, mainly based around common use cases, there is also a RogueLike2d example project for looking at.
First of all it is recommended that you read over the EcsRx Core Docs, which detail the core architecture and ECS pattern etc.
Once you have got all the info on those bits then you can look over the unity specific bits this library offers, there is no real reading order here as its more about how unity bits work on top of the core.