To find it, you need to consult your owner's manual. This is the most reliable source. The manual will show you the fuse box diagrams and locations.
Failing that, you can usually find the fuse box diagrams online by searching "2006 Dodge Ram [your trim level] fuse box diagram" on Google Images or a similar search engine. Look for the diagram that shows the underhood fuse box and/or the interior fuse box (often located under the dash). The horn fuse will usually be labeled, though sometimes it might just be listed as a "horn relay."
