To change the name of a tab, go to your Facebook page and click on Settings in the upper right. Then click on Templates and Tabs. To the lower right on this page you'll see a list of all page apps. On the tab you want to update, click on Settings.
In the new menu that appears for this tab, click on the Edit Settings option that appears in the lower left. To the right of the area titled Custom Tab Name, you will enter your new tab name, then click Save, then Okay.
The name change doesn't show up automatically. To verify the name of your tab is updated, go ahead and refresh your browser. The name of your tab should now be visibly updated.
If helpful here is an 82 second video tutorial: https://www.screencast.com/t/s8USZD2fuVW
Note: Previously we provided this functionality in our app and wish to do so still, but Facebook has limited editing tab name ability to their on Facebook page settings. We are genuinely sorry this is more complicated than necessary.