Open the Files app
Go to the location where you want the folder
Tap the More button
Tap New Folder
Type a folder name
Tap Done
To create a folder on the Home Screen, touch and hold an app
Drag it onto another app
Release to create a folder
Tap the folder name to rename it
Tap outside the folder to finish
To create a folder in Notes, open the Notes app
Tap the Folders button
Tap New Folder
Enter a folder name
Tap Save