All your domains are organized in a table here. You can see previously created domains including the main domain, edit SSL, but also delete, edit and add new domains. Sortable columns of the table include:

Domain - If there is something that needs your attention, you will see a warning icon here
SSL Status - hover over for a tooltip with an explanation of the status
Type: Main Domain, Addon Domain, Subdomain
Document Root path

The Actions on the far right allow you to Edit SSL, Delete Domain and Edit Domain (change Document Root or enable Redirect function).

To Add Domain find the button above the table, then input your new domain and choose its type. To find a specific domain in the table, use the search function nearby.