QNAP NAS secure connection with a Balance 20x

This is my first Peplink router so please be patient with me. I want to establish I secure connection to my QNAP NAS and make sure that the firewall is properly configured to protect the NAS. How do I go about setting up a vpn connection? How do I access my NAS securely using the Balance 20x? Thanks for your input.

the Balance 20x is on the same LAN as your NAS?