At this point, you have two options for creating domain names and their associated description.
You can manually enter the domain name and descriptions into the Domains tab of the geodatabase properties window.
You can utilize the "Table to Domain" tool to import one domain value, coded values, and description at a time.
Issues with Method 1: There is room for error when manually entering the domain name. This could lead to the domain name not matching the attribute table field name.
Issues with Method 2: Though this would address the "entry error' issue above in Method 1, you can only import one domain name at a time and you still have to utilize a "middle man", i.e. the Table to Domain tool.
My suggestion: Utilize the Geodatabase Properties window and Domains tab, but instead of manually entering the Domain Name and Description, have a method by which the empty domain name cells would link directly to the attribute table field names choices and have the description fill in directly from the associated metadata (if completed).
Since this would be linked to the attribute table, you could also automate the entry for field type under domain properties so that it would choose either text, double, float, date, etc...automatically. This also would help prevent errors and save time on the back end.