Domain is another name for web address. If you've previously owned a website or have purchased a domain for your store (ex: www.cityhive.net) then chances are you already have a domain.
If you do not have a domain you can easily get one through using any of these popular registrars: GoDaddy (preferred), Google, & Network Solutions. If your store name is not available, try adding your city or state to make the address more unique.
Finalize the purchase of your new domain and then head over to the next step in the process to invite City Hive to manage your domain. If you think you've purchased a domain in the past but are unsure where your domain is registered, visit this site and type in your URL.