Hi,
Once you have an /e/ account, you can add it in the accounts section of your phone settings.
Then, when clicking on your added /e/ account, you can choose what you want to sync with the cloud as well as CardDAV (contacts) and CalDAV (calendar).
You can view your cloud stuff on this site using your /e/ account credentials.
I don’t remember whether your e.email address configures itself in the mail app once you add it in the phone global settings.
Anyway, here is how to add an e.email address manually to a mail client.
As for "how to do stuff once you have /e/ on it ? Use it like you would use any other smartphone. It’s really user friendly. There’s a set of preinstalled apps that respect your privacy more than Android/Ios but you can install whatever you want from the “Apps” app store. It gives a privacy rating on a scale from 0 to 10 to apps based on the permissions required/trackers. As simple as it gets.
I don’t think there’s a wiki focused on /e/ usage yet. Might be due to the fact it’s still in beta and stuff will likely change.