1) COPY all of the embed HTML code from YouTube, GooglePlus, etc.
2) Go to your Content Page description or Product description HTML editor
3) In the Design view mode of editor write HTML_PLACEHOLDER wherever you want the HTML embed code to be displayed
4) Switch to HTML mode on the editor by clicking the chain link icon in the editor toolbar
5) Locate the text HTML_PLACEHOLDER in the HTML code
6) Select that text totally HTML_PLACEHOLDER
7) Paste over it with the HTML embed code by right clicking and selecting PASTE
8) Save Changes