When I create a customized report, and share it, it lets me share with a group. I created a group. But how do I add users to that group so they can see the cust. rep?

Your confusion ends here, @jb1987.

Allow me to fill you in on everything you need to know about the group option when sharing customized reports.

The Group option only allows you to organize reports, and it doesn't involve any users. Since you want to share the report with your users, you can utilize the Share with option. You'll just need to choose All from the Share with drop-down to let your users view the customized report. I'll attach a screenshot below for your visual reference.

I'm also adding this article to know more about sharing reports: Memorize reports in QuickBooks Online.

You might also want to learn specific ways to customize your reports to get awesome insights. This article will help you with it: Common custom reports in QuickBooks Online.

Please know that I'm just a reply away if you need any further assistance customizing reports in QuickBooks Online. Wishing you continued success, @jb1987.