Step 1 - Generate DKIM and/or Return-Path Record
For DKIM, first you will want to generate a DKIM record from your email provider to add to your DNS. If you are unsure of how to do this, get in touch with the support team of the email provider you want to set up DKIM for so they can point you in the right direction. Each provider you send from will require its own DKIM record be generated and added to your DNS if you want to pass DMARC DKIM alignment.
Similarly, if the sending source you are using supports using a custom return-path, generate a custom return-path record to add to your DNS to achieve DMARC SPF alignment.
Step 2 - Add the generated record(s) to your DNS
DKIM records are added to your DNS as a TXT record and Return-Path records are added as CNAME records. Usually your DNS is managed by your hosting provider, so you would want to head there to add these records. This is not always the case, however. If you are using a DNS provider, such as DNSimple, you would need to add your DKIM and Return-Path records there instead of with your hosting provider.
Once you have the DKIM and/or return-path records generated with your mail provider, below are some links to instructions on adding DNS records for common hosts and DNS providers. If you use a different hosting or DNS provider that you feel should be included here, let us know at email@example.com.