Access front end trying to connect to an SQL backend without the login popping up.

I have an Access database that has been split into a front end and back end.  We recently decided to move the back end to an SQL server.  All seemed to go well but when I open the front end I now have to provide a password and id to log onto the server.  Our users would probably not handle this.

I know there is a way to have the password and id automatically fill that box so that the user never sees it?  

This is not really my forte so you may have to ELI5.  Here are some details

1. We have computers on different domains.  So I was told that the windows authentication would not work.
2. The entire program is internal only so they are not concerned that the password would be hard coded (I warned them against this but they pay the bills, so I do what they say)
3. They have a hodge podge of computers some running os's from 2003 (all windows os's)

I was reading about DSN-less connections and if that would work I would be happy to try (but once again it is not my area, if you know of a video tutorial that would help)

If I am leaving info out please tell me and I will share whatever I am allowed.

Thanks!