Wash and trim the beans, if they are fresh. If they are frozen, cook in water, according to the instructions on the package.
I prefer to steam the beans for 20 minutes, then let cool and drain well.
The beans can be just as easily boiled in water for 15-20 minutes. Then let sit in a colander to drain very well.
Canned beans can also be used, but I don't like the taste, nor the texture - and I mean here the store-bought ones.