This article is for cPanel Accounts. Determine where your account is with this guide.
To enable DKIM for your account, connect to your cPanel account and navigate to the "Email Authentication" page.
From there click the button "Enable" next to DKIM.
This will generate public and private keys to help authenticate mail that you are sending, helping to verify to remote servers that your mail is legitimate.
If you have any questions about this, please contact support!