Here are the instructions as of June 16, 2018:
Open the Facebook app
Click the icon with the three bars in the top right-hand corner of the screen
Scroll down and click on "Settings & Privacy"
Click on "Settings"
Scroll down to "Notifications" and click on "Notification Settings"
Scroll down...
Somehow, my home button no longer takes me to the middle screen like it did when I first bought my phone. I don't know how it happened, but I would like to reset it. And I would like to reset without downloading any additional software. Thanks.