Summarize the following:
This is an easy and effective method for small to medium adjustments, but you shouldn't expect a full-size change. For that, you'll need a shoe stretching liquid and a boot stretcher. This method works because the water will expand when frozen, pushing into the shoe. It has nothing to do with the boots becoming wet, which could shrink or damage them. Fill two Ziploc bags or other freezer-safe plastic bags roughly 1/3 full of water. Squeeze out as much of the air as possible before sealing.  Use a bag that will fit snugly into the part of the boot that needs stretching. A quart (liter) bag works for most toe and heel related adjustments, while you may need a gallon (4 liters) bag to stretch the calf of the boot. To remove the air, seal most of the way and leave a small gap. Gently press the portion of the bag containing air until most of the air has exited and the plastic is nearly flat. Bags not labeled for freezer use may break later in the process, leaking water onto your boots and potentially damaging them. Put each bag of water into one of the boots. If you want to stretch the toe, tilt the boot forward and gently push the bag as far as it will go. If you need to stretch the calf, keep the bag from slipping by stuffing the toe with newspapers. Put your boots in a freezer or icebox and leave them there for 8-12 hours. Unlike most liquids, water expands when it freezes, pushing the boot outward from the inside. If the bag slips out of the toe when you move the boots, tilt the boots forward and prop them up on a block of wood or anything else that will keep them stable. Remove the boots from the freezer and wait for the ice to melt before removing the bags. How long this takes depends on the temperature. Don't try to remove the bags right away, as you could damage the boots trying to pull them out. You should feel a noticeable difference in the stretched area. If it's still insufficient, or if the boot starts to shrink back, you can repeat this method to stretch it out further.
Learn how to use this method properly. Fill two resealable bags partially with water. Push the bags into the area you want to stretch. Leave the boots in a freezer overnight. Thaw for 20 minutes or more. Remove the bags and try on the boots.