To embed a YouTube video on a CMS page, you will want to retrieve the embed code directly from youtube.com. 
  1. Click on the Share link below your video:
          User-added image
  1. Select Embed
  2.  Copy the full embed code:
        User-added image

     4.  Disable the visual editor on the CMS page and paste the embed code.

Note: Please contact the appropriate software vender or IT professional for assistance with this process or issue which is beyond Blackbaud's scope of support.