Wakame is an edible seaweed that contains high levels of iodine, calcium, thiamine, and niacin. It’s different from kombu, and they can’t be substituted with each other. Wakame can be sold dried, salted, or fresh. But you can buy in the United States is cut and dried.
When dried wakame is reconstituted in water for 5~10 minutes, it expands significantly, and is ready to be eaten. Just squeeze water out and use for Japanese style salad with torn lettuce and shredded carrots.
For miso soup, reconstituted wakame is added at the end of the process. This means, don’t boil it.
Wakame can be bought at Japanese grocery stores. Chinese and Korean grocery store usually carry them. If you can’t find it in your neighborhood, here are several links to buy from online;