Scroll down on the left hand side and click "Website"

On this page, you'll scroll all the way down to the bottom where you'll see "Email sending domains (DKIM)"

Add in any email address for your business. It doesn't matter what email you use and long as it's an email with your business domain. 

The system will then generate the records you need to add to your hosting platform. You can easily copy these. 

HubSpot is a CRM platform. Learn how to effectively use HubSpot to manage your customers and other tips and tricks such as how to merge contacts or how to connect your Gmail account.

How to create an Sending Domain in HubSpot