First, I would make sure that your 200 is running ArubaOS 5.x. If it is running 5.x, you can go to Configuration> WLAN/LAN wizard and create an SSID. It will ask you what VLAN to put it on, as well as the encryption. After you choose the encryption, it will allow you to create a role and firewall policies that will determine what a client on that SSID will do. When you are finished making the role, it will allow you to assign that role as the initial role for client that connect to that SSID.