So, I apologize in advance if this is canonized somewhere else, but I couldn't find it on the web anywhere, so I'm happy to share it here:
- One a clear place on your home screen, tap and hold on the wallpaper (not on an icon or existing widget)
- This will load up the homescreen options, tap on the "widgets" box that will appear on the bottom of your screen
- Side-scroll until you see the widget for "Kids mode" - it's a 1x1 icon of a cartoon gator on an yellow background
- Tap and hold the icon and then place it anywhere on the homescreen, this will place the widget icon on your homescreen with a little arrow pointing downward (presumably indicating that this feature still has yet to be downloaded/installed/configured
- Tap on the icon and this will open a new window asking you to install the Kids Mode. Tap on the install button. This will proceed to download the app (reported as being 61.3MB large), and install it (you will see a bunch of toast notifications indicating your internal storage is dropping).
- The screen will then close and take you back to the homescreen where you left the widget - and the little downward pointing arrow should have disappeared.
- Tap the widget icon, then follow the instructions for activating Kids mode!