How to Reshape a Felt Hat

Sans Moisture Recovery

In this case, if the wrinkles primarily affect the crown, you can:

From the inside, push out any dents and wrinkles, using your hand or a hat brush.
Use cloth or a towel to stuff the entire crown area, or place it on a wig stand, if it's available.
Leave the hat in this position for multiple days.
After some time, remove the filling from the crown and see if the hat retains this shape. Going forward, be sure to store your hat in this manner or inside a hat box crown down, and supported with a nest of tissue paper, or even your favorite scarves for the season.

Have either a steamer or tea kettle on hand. Because the emitted steam will be hot, be sure to keep your hands and face a minimum of six inches from the spout. Trust us on this, steam burns hurt!
Once the kettle or steamer starts producing steam, hold the hat beyond this distance within the direction of the steam. Make sure the hat's inside is directly facing you. Otherwise, any interior sweatband will dampen and warp the shape.
As the steam hits the felt, the fibers will start to loosen, becoming more pliable and letting you reshape the material. Once the hat feels nice and toasty, move it out of the steam flow and pull, bend, pinch or lightly stretch the felt to get rid of the wrinkles.
Work through the hat until all wrinkled or folded areas have an even appearance. Generally, it's recommended that you start with the brim and work upward. For cowboy hats, now's your chance to re-curve the brim. With the crown, always reshape from the inside, pushing outward.
Once you're done, let the material cool before placing it on your head to fit its shape. Keep it in place for a few minutes, so the crown can conform to your head's curves.