How to make your own custom hats?

I was wondering how other people got hats that you couldnt buy in shops...So now im here to ask. If you know how to please respond to this thanks!

This should only happen if they either won a special event when a rare hat was offered as the prize or if they were allowed to upload a hat due to some work they assisted with on the server. Generally we do not allow this so it would have to be from one of these rare occasions unless it is a hat that was sold at one point but the shop has since closed.