Connect your domain

To send emails, it is required to connect your domain. To do this, go to your dashboard, navigate to 'Domains,' and click on 'Add domain.'

Follow the steps provided.

Verifying the domain with your DNS provider

After you’ve added your domain, you must complete the verification process with your DNS provider

You can check how to add the records to your provider via these links

GoDaddy	https://www.godaddy.com/help/add-a-cname-record-19236
Namecheap	https://www.namecheap.com/support/knowledgebase/article.aspx/317/2237/how-do-i-add-txtspfdkimdmarc-records-for-my-domain
DreamHost	https://help.dreamhost.com/hc/en-us/articles/215414867-How-do-I-add-custom-DNS-records-
Cloudflare	https://support.cloudflare.com/hc/en-us/articles/360019093151
HostGator	https://www.hostgator.com/help/article/manage-dns-records-with-hostgatorenom
Names.co.uk	https://www.names.co.uk/support/1156-changing_your_domains_dns_settings.html