Months ago I was looking for those same thing, I read the doc but wasnt clear enough I had to follow tutorials not until I learnt it, now I use it on all my project, which i added django allauth but i recommend reading this and following this tutorial, if you a newbie custom user model can be a pain in the ass
https://testdriven.io/blog/django-custom-user-model/ read and follow this tutorial,if you dont understand I can give you a github repo which I do copy from to start other project