I love showing Halter. Which Im assuming that is what you will be doing with Howdy. And not Showmanship.
First of all Halter is basically all about the horse. Whereas showmanship is more about the handler.

He needs to be slicked up. Id recommend a FULL body clip 2-3 weeks prior to the show. Is he still "fuzzy"? Cant have that either.

The judge will require you to do trotting on a lead line, halts, and walking.
Its hard for me to show you through this on the forum. You usually cannot use just a regular halter, most shows require a show halter (leather with silver).

I usually dont start showing my weanlings until they are about 6 -8 months. Thats because I take the time to have them fitted and conditioned.

You'll need to check with the management of the show to find out their rules and regulations. Most "open" shows around here still follow AQHA and APHA guidelines. Proper attire is a must and the horses of course must follow as well.
You can PM me with any other questions you have, Id be glad to help ya.
Brittany