You can either create a new station or add a mountpoint on the settings of your radio station in the Shoutcast Radio Manager.
Click on "New stream" under :
1- Shoutcast For Business users:
You can add one mountpoint 64 kbps (AAC or MP3). If your main stream is already a 64 kbps flux you can then create an additional one of the format/bitrate of your choice.
2- Shoutcast Server Software
You can add as many mountpoints as you wish.