Custom domains can be used for your Storefront. Please note, to do this you will need to have a domain provided through another service, such as GoDaddy. Further, the page will need to be set up with CNAME forwarding. For help with this, please reach out to the support desk of your domain provider, as each provider may have a different way of getting CNAME forwarding set up.
To start, click on the gear in the upper right and choose Settings.
From here, click on Storefront.
In the first set of options in the upper left, you will see a box that you can put your custom domain in.
Again, please note that you will need to set up CNAME forwarding on your domain for this page.