-Remove any mastering/limiting/compression from the overall master buss
-Make sure the master buss (overall mix) doesn't peak beyond 0db at any point. Reduce the master fader leaving 3-4dB of headroom
-Export the mix as a mixed, stereo 24 or 32bit WAV or AIFF file.
-Send us your File by using Google Drive, Dropbox, We Transfer to email@example.com