Custom Pages vs New Users

Until recently I have been the only user. I created a custom page to the Admin Page to allow me to edit content on my site.

I now want to add other users. I created a new user and gave them the very lowest ranking possible. Everything is as it should be excpet they can see the custom page I made. (As part of the standard admin menu).

How would I go about setting user ranking to my custom page.

TIA