My domain is registered on cloudflare.
So go to https://dash.cloudflare.com/profile/api-tokens to either use global key
or better create a new api key for a specific zone with zone dns edit permissions.
Copy that token you just created. Go back to dashboard, click on the domain you want to use
bottom right corner copy the zone id.
Acme Client I have used
https://github.com/acmesh-official/acme.sh