Your subdomain is automatically created using your Business Name, but can be edited at any time.
Step 1: Click Account from your dashboard.
Step 2: Click Settings to open up your Business and Account Settings.
Step 3: Click Business Information.
Step 4: Edit the Subdomain and click Save.
To do so, go to your form and grab the new embed code on the Publish tab. Replace the current code on your site and you'll be all set!