If you have bought a pair of shoes that are too big in the heels, that may be because you have differences in the size of your feet, or the shoes just don't fit properly. However, if you love the shoes and don't want to part with them, there are some ways to make it so that they fit better and you can continue to wear them.
Place the insoles in the bottom of the shoes that are two big. You don't need to affix them to the shoes in any way. There are insoles that are specifically for athletic shoes and others that are for casual and dressy shoes.
Put leather or silicone heel grips in the back of the shoes to prevent heels from slipping. Peel the backing off of the heel grips, and press them into the back of the heel with the curved part pointing down.
Place the heel grips in the central part of the heel. Do not wear the shoes until 24 hours have passed after you put the heel grips in the shoes.
Don't run or do any high-impact exercise if your shoes do not fit properly.