From the Settings app, tap Accessibility.
Scroll to and tap Assistive Access.
Tap Set Up Assistive Access.
Tap Continue.
Tap Continue again.
Select your appearance option and tap Continue.
Select the app you would like to have optimized.
Choose your preferences for the app and tap Continue.
Tap Continue again.
Tap Continue again.
Tap Continue again.
Tap Start Using Assistive Access.
Enter a passcode.
To exit Assistive Access, press the power button three times, then enter the passcode you created during the setup.
You've completed the steps!
