[dba-SQLServer] I'm getting nowhere

I am getting nowhere on understanding SQL Server security.  Microsoft provides us with SQL Server 
Express which implies that joe blow (me) is going to install / maintain it.

I am not a SQL Server Admin and I cannot afford to spend the time to be one.

Google is my friend.  BOL is not.

Except that Google is taking me to these places where I am expected to already know how this stuff 
works, and then wants to make me a *better* administrator.  Which of course is useless because I am 
not an administrator at all.

OTOH I am not stupid.  If I could find something that started at the "This is SQL Server security" 
basics I could learn this stuff.  Before anyone says "RTFM (BOL)" let me simply say, "not 
happening".  I have tried BOL and it simply sucks for my level of expertise (my opinion of course). 
  If that is your advice, simply stay out of this thread.  Thanks!

So... my needs:

I need to set up several SQL Server databases for use by different, very small groups (5-20 people) 
of entirely unrelated people.  What I mean by that is that each DB is for a different "company" if 
you will.  I need to access these databases from C#.  I understand the group / user paradigm.  I 
would like to create groups and users.  Specific groups can do specific things in the database, some 
can see data but not modify it.  Some can add records in specific tables but not others.  Some can 
run reports (view).

I do *NOT* want to create windows level groups and users if I can avoid it.  These are people that I 
do not necessarily know and I do not want to give them any rights at the machine level, and I prefer 
to not maintain such lists at the machine level.

Unfortunately SQL Server does not seem to model Groups / users.  I go into SQL Server and see a 
security tab.  It has "logins".  Is that a user?  A specific ability to log in with a password?  To 
what?  The server itself?  A specific database?  Groups of databases?

I see "roles" but these appear to be aimed at the server and none of these people are going to be 
doing anything at the server level.

Can I safely ignore everything under the server security tab?

I go to a database and I see a security tab.  It has users and roles.  Hmm... better (I would 
think).  I would like to add users "under" the specific database that the user will access.

So I try to add a new user but I do not see anywhere to require a password.  Hmmm...

I go into roles and I do not see any predefined role that looks like it would be useful to me in 
meeting my needs described above.  If I look at "add new role" it asks for a password.  The User / 
group model does nto assign passwords at the group level which implies that a role is not a group at 
the user / group paradigm.

Is it just me, or is SQL Server security just... different?  Am I correct in assuming that it 
doesn't implement a user / group paradigm?

And more importantly, where can I go to get a plain, simple, English description of how this mess works?

And please excuse the tone that results from my frustration.  The only help documents that I have 
found (and I have extensive lists of bookmarked web pages) so far assume that I am an administrator. 
  I am not, and cannot afford to become one.  And yet MS pushes SQL Express as if I (non-admin) 
should be able to use this as a data store pool.

Help!

-- 
John W. Colby
www.ColbyConsulting.com