The Photos app automatically finds most of the photos and videos on your PC and OneDrive. But if it’s missing a folder full of photos, you might need to tell it where to look.
Open the Photos app and select More > Settings.
Under Sources, select Add a folder .
Browse to a folder on your PC, an external drive, or a network drive connected to your PC, and then select Add this folder to Pictures. Subfolders of the folders you add are included too.