There are several ways to do this:
You can connect your laptop media player to the MP3 stream and then connect your headset output port from your laptop to the correct port on your PA system.
- Smart Phone
The same principals apply as with your laptop. The benefit to using a smart phone is that you probably have a data connection on it already. However, you need to be sure the data connection is fast enough to handle the MP3 stream and that your data plan has sufficient data included.
- Barix Exstreamer
If this is something you will be doing on a regular basis it would be worth considering purchasing a Barix Exstreamer. This standalone box will require a network connection and can be easily configured to point to an MP3 stream.
The EasyStream devices come with an audio output port that can be connected to your mixer. Once that is in place the audio can be controlled via the devices onboard web interface.