I installed the Unbubble.eu add-on, but don't see in in my Plugins or Extenions....where is it. I tried installing again and got an error message saying "engine with the same name already exists." So once again....where is it.....can't find it anywhere......so how do I use it?
It sounds like you installed an OpenSearch add-on, which only adds a search engine to the search box (next to the URL textbox). If you click on it, you should see it as an option in the dropdown.