Sorry for this late response, but I don't wander over here too often.
To add wiki or free dictionary: Go to Tools>Add-ons. This opens up the box for add-ons that should have Cooliris (the overall program is called Cooliris with Coolpreviews a part, I believe) installed. Click anywhere on the 'Cooliris Previews' section, and choices become available. Select 'Options' and click on tab for 'Right-click search'. Here, you will see two boxes ('Non-Activated Websites' and 'Activated Websites') with arrows going back and forth. Certain activated websites come loaded with the program, like Ask.com, YahooImages, Flickr, and of course, thefreedictionary or Wikipedia. Simply click on the one you want in the non-activated, and hit the arrow going to the activated box. To remove, just reverse. I think you may have to restart your browser before they appear, I can't remember. Now you should see these options available as part of your right-click menu when you highlight a word or phrase.
You can also supposedly customize it for any website that has a search engine, although I personally haven't done that. Similar instructions with images are here:
http://www.coolpreviews.com/firefox/right_click_search.php