Please send it in a single zip via the uploader that we provide on your project page.
Make sure you name the audio files so that they clearly indicate on which side and track number the audio goes to.
e.g. A1 Example.wav, B2 Sample.wav
With in your audio zip please also include your track lists to confirm the music that you will be pressing.
If you are not sure about this, you can download the track list template here.