Open IT Online is a Firefox extension and, as any other extension, you can uninstall it doing click on Tools > Addons, then click on Extensions, select Open IT Online and finally click the Uninstall button.

However, we would like to know why do you desire to remove Open IT Online: what didn't you like? Could you please take one minute of your time to make a post on the official forum, so that we can take your feedback into consideration to improve Open IT Online.