Read about Personal Vault and select Next or Continue (It varies depending on your device).

If you don't see the message or you dismissed it, browse to your OneDrive and select the Personal Vault folder. The first time you see Personal Vault in your OneDrive, you'll see a message where you can select Get started. You’ll need to set it up separately on each device where you want to use it. Personal Vault is a special folder in your OneDrive that’s protected by an extra layer of security. All your documents, photos, and videos in Personal Vault are easy to access from, your PC, or other capable devices. Personal Vault automatically locks after a period of inactivity and then you need to unlock it to get at your files again. Personal Vault is available from OneDrive on the web, the mobile app, and from your Windows 10 PC. You can download Sysinternals Process Explorer here.Personal Vault is available for OneDrive home and personal plans, not available in OneDrive for business, or work and school accounts. Proceed with care when deleting handles as this may generate erratic behavior and instabilities may occur. Selecting the process/handle/program entry.An individual program or handle in the list provided by Process Explorer can be killed by: To release the lock on the file you are attempting the maintenance operation on, you will need to kill the appropriate process. Type in the name of the locked file or other file of interest.Alternatively, click the “Find” menu and select “Find a Handle or DLL”.Identify which handle or DLL is using a file The executable that is using the file will be highlighted in the Process Explorer main display list.Drag the icon and drop it on the open file or folder that is locked.On the toolbar, find the gunsight icon on the right.Using Process Explorer there is a simple way to find the program: One of the easiest ways to handle locked files or folders is to use Microsoft Sysinternals Process Explorer. 'Make sure the disk is not full or write-protected and that the file is not currently in use'.'The file is in use by another program or user'.'The source or destination file may be in use'.

'Cannot delete file: Access is denied'.When trying to delete, move, or rename a file you get a Windows system warning message:

How to lock a folder in windows