On line 22:
5. If you are using the domain for any other websites copy the records below (if you are just using the domain for BlueBubbles you can skip this part)
There don't seem to be any records below to copy.
(Additionally--and this is probably just a point of confusion for me, personally--this is implying that BlueBubbles can run on a subdomain, just that Cloudflare needs the domain itself added, as stated in line 20. Correct?)