As an Admin, transferring ownership of your domain is a straightforward process. If you already have multiple admins, no action is required. Simply ask one of the other admins to remove you from the domain by accessing the members' section within the Settings page.
However, if you are the only Admin, you will first need to grant Admin permissions to another member. You can do this by going to Settings, clicking "Members" and changing a member's role from the dropdown beside their name. Once this is done, that member, with their new privileges, can then remove you from the domain.