DMARCLY’s API uses a simple HTTP Authorization header with an API key to authenticate you.
To get your API key: log in to the DMARCLY dashboard, then go to System => API Access (this one below is fake):
You can then make requests against the DMARCLY API endpoint like so:
curl -H "Authorization: Bearer 8af9a3411159d108907937250dc1569d" "https://dmarcly.com/api/aggregate_by_domain?start=0&end=1811111112"
Note that API access is available to the Enterprise plan only.