You don't need to configure anything for your files (in the My Files folder) to get synced automatically.
Network Folders are not synced automatically by default
Network Folders typically store very large amounts of data.
The Sync app, therefore, doesn't try to synchronize them automatically to the local machine where storage might not be available for a large amount of data.
If you need to synchronize Network Folders for offline access, you can - just make sure you have enough storage space
What do you want to do?
Learn about Offline Access
Working with Offline Access
Setting Advanced Offline Access Options