Like I said, unless you live in the proper areas in the world to breed them, you won't find much success. Seeing as how you basically need to make a compost-type bin out in your backyard and fill it with your scrap food items from the house, release your flies outside. They will stick around as long as your in the right area of the world, and the food is present.
Of course that is very general, but figured that right there puts off about 90% of people. If your still up for it, I can go dig around and find an indepth guide for you. There are also guides on youtube.
-Brandon