How to set up user login/ registration?
it's not too difficult - but make sure you are using the very latest version on 5.7 as some of the earlier versions had specific problems with Registration.
If you don't want to do anything too ambitious then you can go to:
System and Settings > Login and registration
the options there are fairly self-explanatory.
once a user registers they automatically become part of the registered users group.
You can then use permissions to block view rights to 'Guest' and allow view rights to 'Registered Users' for selected pages / branches of your sitemap.
This gives you the basis for members only pages. If you want to do anything more complex you'll likely need to look at Advanced permissions.
I'll have a good read thru this and the links you've supplied and see how i get on. Thanks again :)
You have to configure /application/config/app.php :