See our technote here for complete process.

4. In this screen, you will add the record information. Follow the steps below:

A) Name: This will be the identifier for your record. It is important to note, the domain name is automatically appended to the “Name” field of the record.
B) TTL: Edit the TTL. Time to Live is measured in seconds and is the amount of time the record will cache in resolving name servers and web browsers.
C) Providers: In the drop down menu choose your CA (certificate authority) provider. The hostname of your provider will automatically populate the Value box. If your provider is not listed, then choose other, and enter the hostname of the provider in the Value box.
D) Tag: Tags allow you to choose how you want certificates to be issued by the CA. Each CAA record can contain only one tag-value pair. Refer to the Configuration section for more details on the kinds of tags.
E) Note: Add a helpful note with keywords so you can search for your records later.
F) Save and Close: Save your changes. Don’t forget to commit your changes.