The Website Is Open
The New Horizons website is open, and so are accounts. You can make yours today. It's free, and the same account will work on this site and in the game.
The Game Is Coming Soon
The game isn't open yet. It will begin with a closed alpha for a small crew of testers, and each tester needs a key. We aren't giving a date: it will open when it's ready, and we'll say so here first.
If You're Given a Key
Log in and enter the key on your account page. An alpha key stays good through the beta that follows.