Most vegetables can be blanched with either boiling water or steam. The amount of time will depend on the vegetable, but 2-4 minutes is usually enough. I will provide an example below.
Put a large pot of water on the stove and bring to a boil. Fill another large bowl with ice water.
Wash beans and snap off ends and string if necessary.
You leave the beans whole or cut them to your desired length.
Once the water is boiling, drop the beans in and set the timer for 3 minutes.
When the timer goes off remove the beans with a slotted spoon or spider strainer and plunge them into the bowl of ice water to stop the cooking process. Once cool drain in a colander.
Lay the beans on a lined cookie sheet and freeze. Once frozen put them in a ziplock, remove as much air as possible and freeze.