That code is for html or something, not for vBulletin. (The forum software is called vBulletin)
Clickicon and paste in the URL and click ok. Type the text you want to show (e.g "Minecraft boredom?") inside the tags. Click preview to see if it is working etc.
This is how it will look.
Minecraft boredom?
Quote this post to see how I did it, if you are still confused.