All good web authoring software has the ability to insert snippets of HTML. This is often under the Insert menu. For example Microsoft FrontPage has an option Insert -> Advanced -> HTML where you can simply paste the HTML snippet.

You can find out more here:
http://www.xaraonline.com/home/support/insertingamodule.htm

Note: It is necessary to preview your web page in order to see the add-on or Module in action.