Braille support can now be toggled with a single keyboard shortcut. Learn More.
Go to INSERT
Find 'Upload' - clicking will open up your computer's document finder
Find 'Google Drive' - you can add docs from your Drive (your drive or from shared docs)
Find 'Google Docs' - you can add docs from Docs, Slides, Sheets, Forms, or Charts
For Google - click on desired doc and hit the blue INSERT
Go to PAGES
Decide which main page you want to add a sub-page to
Click on the 3 vertical dots on the right side of the page
Click on 'add sub-page'
Name your page accordingly and hit 'done'