How to replace the back glass of the iphone 5?

I'm wondering on how do you replace the 2 back glass that is on the back of the iphone 5? Do you have the disassemble the whole iphone? Or just apply heat onto the broken glass? And then remove it and then place the new ones? And if you have to disassemble the whole iphone why is that?

Easier Answer -
Take it to the shop. Therefore, you know if anything goes wrong the shop will have to repair or replace your phone. If you do it 'DIY' and something goes wrong its gonna cost you more.

The back of the iPhone 5 doesn't have glass, its aluminum. Take it to a shop