I am trying to set up a development environment on a local machine and am having issues.  I was hoping someone could answer some basic SQL Server questions, as it seems that   the way to configure IIS has changed since the lat time I did this.

The database is named "dnndev.me" and the user is named "dnndev"

1. There are two locations in the database for users/logins. one under "\security\logins" and another under "/dnndev.me/security/users".
The user "dndnev" is listed in "\security\users" but not in "\dnndev.me\security\logins".
there is a user "dbo" under "\dnndev.me\security\logins" but not under "\security\users"
The properties-user mapping for user "dnndev" has the db_owner shema checked.  There is no 'dbo" schema to check.
"dbo" is listed as a user under  "\dnndev.me\security\users" but "dnndev" is not.  When I try to add add "dnndev", I get an error saying a user with that name already exists.
If I log into SSMS as dnndev and create a table, it is listed as dn_owner.test instead of dbo.test

There is obviously some relationship between the users listed iuneder "users" and those listed under "logins", but I don't udnerstand what it is.

Can someone explain the relationship as well as how to create/configure my user "dnndev" so that DNN works properly.
there is also a user "IIS Apppool/dnndev.me" which reflects the name of the application pool configured for this application.  I assume that there should be some configuration related to that user as well.  Any help would be appreciated.

(this is windows 10 prof, SQL Server 2016, DNN 8.xx )