help with docker stack and dns record setup

[m0t0k0-2501]

Hello, I'm pretty new with docker and I'm trying to create a stack, this is what i have in my .yml

version: '3.8'

services:

        ddns:
                image: davd/docker-ddns:latest
                environment:
                        - "RECORD_TTL: 60"
                        - "ZONE: domain.com"
                        - "SHARED_SECRET: secret"
                ports:
                        - "80:8080"
                        - "53:53"
                        - "53:53/udp"

the service error is telling me that the SHARED_SECRET isn't set, this is the error message:
| SHARED_SECRET not set
| Starting domain name service...: bind9.
| panic: open /etc/dyndns.json: no such file or directory

(I'm guessing its looking for that directory in the container?)

anyway, other than this, I was reading some other issues on this github and I'm guessing im supposed to create an A record called ns.domain.com and also a NS record that points to this container at ddns.domain.com?

I'm using namecheap so would this be right?

If so I'm a little confused as to how namecheap would know what ddns.domain.com is, would i also have to create an A record saying that ddns.domain.com is the same host as ns.domain.com???