After following the guide to create a basic DMARC record you will be able to add MTA-STS reporting and MTA-STS file hosting.
We will host your MTA-STS policy at https://mta-sts.example.com/.well-known/mta-sts.txt We will host and provision a LetsEncrypt SSL certificate on your behalf. Our company is a multi-year sponsor of the letsencrypt.org project.
The next step will require access to your DNS so you can create TXT records.
Once published you can validate your MTA-STS record is published by checking with this tool - https://aykevl.nl/apps/mta-sts/