You can sync your SharePoint Online files to a folder on your computer where you can work directly in File Explorer and access the files even when you're offline. When you're online, any changes that you or others make in the document library will sync between your document library and your computer.
Note: If your environment doesn't look like these screen shots, see Sync site libraries to your computer for syncing libraries on your version.
Sync your document library files with your computer
Open the document library you want to sync.
Click the Sync button.
At the prompt, click Sync Now to start the sync app.
The first time you run it, the sync app automatically fills in the name and web address of the library.
If you're using Windows 10 Edge browser, you may be prompted to switch apps to OneDrive for Business. Click Yes to continue.
Once SharePoint Online is syncing your files, click Show my files… to open the folder on your computer in File Explorer.
The synced folder is listed in Windows under Quick access, in the SharePoint folder.
Once you've set up a synced folder, you can save files directly from desktop apps, or copy files into the folder to be synced with your online document library.
When you're opening or saving an Office 365 document from your computer to the sync folder, your screen looks similar to this:
To stop syncing a library
If you no longer want to sync a document library with your computer, you can stop the sync from your PC. See Stop syncing a library for steps on how to do this.
Share a file you're syncing
You can also share files that you're syncing from your computer. See Share OneDrive files and folders for more information.