You play BYOND games on your Windows PC, using the free BYOND software. Once BYOND is installed, all you have to do is find a game to play. There are two ways to play: Either download a game and play it by yourself, or join a live game with other BYOND players who are online.
Players on BYOND have the option of creating a free user account, which gives them an identity other than "Guest" to use online. You can do that now, or at any time you like later on.