DKIM Code its valid but not in the mail header

Hello i use the Virtualmin to create the DKIM code its a validated, i used an external site to test it to make sure the dns records are correct. they are all validated. But when i sent out the mail testers + my personal email there is not mention of dkim at all so that part of the test failed

Also on the side not as important one of the test recommended adding list unsubscribe to the header. how do i do that if i am sending email using usermin

Oh yeh at one stag DKIM was giving me erros so i reinstalled it

Is the opendkim service running on your server?

yeh it is

opendkim.service - OpenDKIM DomainKeys Identified Mail (DKIM) Milter
Loaded: loaded (/lib/systemd/system/opendkim.service; enabled; vendor preset:
Active: active (running) since Mon 2018-06-11 11:46:28 UTC; 3min 0s ago
Docs: man:opendkim(8)
Process: 17768 ExecStart=/usr/sbin/opendkim -x /etc/opendkim.conf (code=exited
Main PID: 17770 (opendkim)
Tasks: 6 (limit: 4915)
CGroup: /system.slice/opendkim.service
└─17770 /usr/sbin/opendkim -x /etc/opendkim.conf

yep, i think i need to hook it up with Postfix somehow?