A subdomain is the first portion of the URL that is present across all of your pages in your account. For example:
WARNING: Changing a subdomain will break any existing URLs. So proceed with caution. After updating a subdomain, you'll need to go republish any previously published pages. This is rarely done. Typically only in the case of a spelling error or to shorten the subdomain.
To update your subdomain, follow these steps:
Hover your mouse over the gear icon in the upper-right-hand corner of your account
Select Organization Details from the dropdown menu
Click the Edit Settings button
Scroll down to edit the Subdomain
Click the Save button
Also, if you are interested in removing RedPodium from your page URL, you are welcome to check out our Custom Domain feature here.