I've downloaded and [I think] installed them, but I can't find the mystical "Maps" button that I've seen mentioned somewhere ("click the Maps button"). Please help. Using Basecamp on a Mac.
For starters, you are in full-screen mode and the menus are not shown there. Either exit full-screen mode, or just point your mouse at the top of the screen to show the menus. You will then see the Maps menu.
If you want a "maps button", use the View > Customize Toolbar menu and drag "Currently displayed map" to the toolbar.