Sayamusume
Edamame in the US

You want to direct sow your edamame seeds straight into the ground once all danger of last frost has passed, and the soil has really warmed up. For folks in colder spots like USDA Zone 3, that'll be June or July, but if you're in Zone 9 or 10, you can get started as early as February or March, and keep sowing right through summer. Plant the seeds about 1 inch deep and space them 3-4 inches apart in rows, with about 2-3 feet between rows. If you can get hold of it, inoculating the seeds with a nitrogen-fixing bacteria before you sow them will give you the best results, like I say, it's a real boost for the plants.

Once your edamame seedlings are up and growing, you might want to thin them out a bit to about 6 inches apart, giving each plant a bit of room to spread its roots and produce plenty of pods. They don't usually need any kind of fancy support, they're quite bushy plants, which is handy. You can even grow them in containers if you're a bit short on space, just make sure the pot is a decent size for them to thrive. Remember, they're nitrogen fixers, so don't be tempted to over-fertilize them with nitrogen, or you'll get lots of leaves and not many beans.