Click on the link below:
https://support.office.com/en-us/article/video-sync-files-with-onedrive-files-on-demand-1ab17c60-af03-4c63-a24c-bb1e131f76c9Sync files with Files on Demand
Select the white or blue OneDrive cloud icon in the Windows notification area. Right click onto the cloud icon and select Settings.
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The Settings menu will open and make sure to tick “Save space and download files as you use them” under Files on Demand.
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Status Icons
After Files on Demand is on, new status icons are shown next to each of your Sharepoint Files.
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Save space on your device by making files online-only.
These files are only available when you're connected to the Internet, but don't take up space on your computer.
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When you open an online-only file, it downloads to your device and becomes locally available.
You can open a locally available file at any time even without Internet access.
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To make a file always available, even when you're offline:
Right-click it and select Always keep on this device.
To change a file back to an online-only file:
Right-click it and select Free up space.