Heat treatment

Could do with being educated, please.
I've got some skates (to go with my quad skates) and both boots press against the inside corner of my big toes - so it's quite painful.
The boots are moulded plastic at the front; I have learnt that they are hockey boots, but when you're buying in a small Austrian town just before Christmas and the only source is InterSport, that's what you end up with. Made by Firefly, by the way - please don't take the mickey!
I've read on here of people using heat treatment to adjust the fit of the boots. Can somebody let me know what is involved, please?
Thanks in advance.