Via OneDrive App:
Swipe down the file or folder to select it, and then tap or click “Make offline.” If you are worried about using too much space on your PC, make fewer files available offline. If there are files you no longer need to use when you are offline, change them back to online-only.
If space on your PC isn't a concern, you can also make your entire OneDrive available offline.
- From within the OneDrive app, swipe in from the right edge of the screen, and then tap “Settings.”
- Tap or click “Options,” and then turn on “Access all my OneDrive files offline.”
Via File Explorer:
Press and hold the file, and then choose “Make available offline.” To make your entire OneDrive available offline, press and hold OneDrive in the left pane, and then choose “Make available offline” on the drop-down menu.