Friendly URLs in NetCommunity can be setup using a directory, using the main website's domain. Example:
Main domain:
Directory: /mypage

A friendly URL is customizing the directory portion of the URL and redirecting it to a different page. If you want to completely replace the long URL with a short URL for a specific page

You can redirect the friendly URL to an existing page on the NetCommunity website or to an external URL.

To setup a friendly URL:

  1. Log in to the NetCommunity website
  2. Navigate to Site Explorer>Friendly URLs
  3. Click New URL
  4. Under Friendly URL, enter the directory you'd like to use and click Check Availability. If you receive a Success message, continue with the steps
  5. Under Target, select the radio button for Select Page, if you're redirecting to a page on the NetCommunity website, or Enter URL if you're redirecting to an external URL or possibly for a URL that isn't a NetCommunity, like a document
  6. When finished, click Save

Note: friendly URLs must be added one at a time. 

Additional resources:
IChange the Site URL in Blackbaud NetCommunity