How do I do the DKIM setting for my Nurture account?

After adding your sending domain in Settings under Sending domains tab. Click on View button in DKIM column for that particular record, then a popup will appear. Add a new TXT record on your DNC hosting panel with the name nurturehqmail._domainkey.yourdomain.com (just replace yourdomain.com with the domain you're setting up). The value for the record is the value displayed on the popup.