DKIM, DMARC setup for MX Plan

Hi, I tested my email account: https://www.mail-tester.com/

I don't have DKIM. I tried something a few months ago but it did not seem to work.
I'm thousand miles from my expertise.
I could see explanations for OVH Exchange but I have the MX Plan.
I don't know how to proceed to get the DKIM working.

I have SPF but both DFP and DKIM seem to be needed to then work on DMARC.
I also don't know how to set it up.

As I was capturing my setup I saw this message: zone xxformat.com/IN: _sip._tls.xxformat.com/SRV 'sipdir.online.lync.com' (out of zone) has no addresses records (A or AAAA)
I don't know why it occurs now, what's the consequence for it and how to fix it.

I wish it would just be setup by default by OVH.

Any tip would be really valuable to me.
Regards