Thanks, but it seems this title is embedded into the Activity module added by a plugin. How would I change the text from Site-Wide Activity to what I want?

Dear ngraddon!
You should be able to make any changes you want as long as you don't want to change the name of your page. You even change the route that the page woill tke when opens. And as MarineMom says, do not ry to change the provacy policy because you can't. I hope this resolves your issues. Keep working hard. I am glad you are making progress.

Thanks but not quite my issue. I want to keep the page and change the text. It read Site-Wide Activity and I want to change that text to something else.

Everything except the privacy policy. If you go to Appearance -> Menus - you can remove the pages from the menu listed there.

Click on "save menu" when you've done that - and all the menu items will be gone.