@thezfunk
Your nearly done, I guess.
You saw it : https://github.com/acmesh-official/acme.sh/wiki/dnsapi#dns_namecheap
And of course the namecheap acme.sh documentation.
Fill in the domain name, like "pfsense.domain.tld" (you rent domain.tld - right).
The the API key
Get the user name.
My advice : set DNS Sleep to "120" seconds.
And you should be good.
For namecheap stories, use the forum search button, and search in the pfsense acme.sh sub forum.
Not this one, as for some reason you posted here but the question isn't "General" at all, and acme has its own forum dedicated to the acme.sh package - let me highlight it for you :
a77c8154-d11f-4a80-97da-41bbddf6913f-image.png