Kombu comes in strips about 8 inches long. All you do is break a strip in half, throw it in your beans when you're soaking, and leave it with the beans until they're completely cooked. When the beans are finished, the kombu will be slimy and stringy--you can either chop that up and throw it back in the beans or throw it out. That's it! Easy peasy!
I've never heard of putting it even in the soaking water. We just toss it in, when I put the beans on to cook. Still slimy and all, but great compost! Just used it in rice tonight, as it adds nutritional value to anything