Before accessing shared folders from Windows, make sure the relative file sharing protocols have been enabled for your Synology NAS.
To access shared folders from Windows, you can use either of these methods:
1. Use Synology Assistant to map the shared folders as network drives.
Run Synology Assistant (available at Synology’s Download Center), select the server from the server list, click Map Drive, and follow the onscreen steps. After that, you can access the mapped shared folder directly in Windows Explorer.
2. Use Windows Explorer.
Open a Windows Explorer window and choose Tools > Map network drive. Choose a drive number from the Drive drop-down menu. Then enter:
\\Synology_Server_Name\Shared_Folder_Name
in the Folder field, or click Browse to locate the shared folder. Enter your DSM user name and password, then click OK.
If you still cannot access the shared folder, the knowledge base also says to check shared folder permissions in File Station with an account belonging to the administrators group, or ask an administrator to adjust the permissions.
Used sources: [1], [9]