Can use the hairdryer trick as long as you keep an eye on things as they are heating up. Steal (or borrow) your sister's or mom's hairdryer (preferably with a relatively long nozzle) and shove it down your boots on the highest heat setting. Let it heat up for a few minutes and then put your foot down in there, buckle up and keep your boots on for 10 minutes or so. Just don't leave it running in the bathroom or something and forget about it.
You just bought a boot with an Intuition liner, of which of its main benefits is being able to be custom fit to your foot. Since fit is the most important part of a boot, don't chince out and potentially risk not doing it right. Take it to a shop to have professionally done so your feet can be happy. Shouldn't cost you more than $40 but $40 to make the boot fit really well and have it last your for years is a very small price to pay.