Forward a Subdomain to Synology NAS

Hi all, this may be a simple question with an easy answer, but, alas, here I am.

First, environment:

Synology RS818+

Barracuda F280 (with static IP address)

Domain hosted by 1&1

I want to forward a subdomain (nas.example.com) to our Synology NAS, but I'm kind of hung up on how to do so. Is it as simple as creating the subdomain with our domain host, creating an A record that points to the static IP which the Synology sits behind, then create a destination NAT rule on the firewall?