In order to blanche veggies, you need a big stock pot full of boiling water, about 1 gallon for each pound of green beans (this will work with wax beans also). You should wash the beans first and trim them, remove any strings and cut them into the size you want, usually between 2 and 4 inches. I like mine a little shorter, about 1 1/2 inches.
Once the water's boiling and the beans are ready, just dump them in and let them cook for 3 minutes. You should prepare a bowl with icy water, too. When the 3 minutes are up, scoop out the beans and dump them into the ice water bath. This is called "shocking" the beans. Leave them in the bath for 3 minutes also.
After the beans are drained, lay them out on some kitchen towels or paper towels to help soak up most of the excess water. Then put the beans in a container (I use a freezer bag), pack them closely without mashing them, leave some small amount of head space (breathing room) and put them in the freezer! They'll be good for 8 to 10 months this way.
To cook, take some beans out, put them in a pan with a little salted water and cook for 5-6 minutes. Here's a video I found over at YouTube that is only 2 minutes long that illustrates the process:
Blanching vegetables when they are in season (and less expensive) is a good way to eat fresher food at a lower cost than buying prepared vegetables. Bon Apetit!