The HIVE-numbers are from the new communities - if you use the Hive-number as your first tag it will show up in that communities community page. I belong to a few communities.
Natural medicine is hive-120078 there trending page is https://beta.steemit.com/trending/hive-120078
You can view different communities on the left hand menu and subscribe to them then they will show up in your communities on the left hand menu.
Powerhousecreatives is hive-114105
Go to https://beta.steemit.com and sign in just like you would on steemit then join some communities and carry on from there.
Sorry I don't have a link for further reading. I learned most from the Natural Medicine discord server.
Hope that helps!
Have a Happy New Year!