Mackie MP-320 Owner's Manual page 11

4. Carefully insert the in-ear
monitors into your ears.
The L/R markings are
located on the inside of the
in-ear monitors where the
flexible over-ear piece meets
the in-ear monitor.
5. The cable may be located
on your front or rear side.
6. Raise the volume on your
device up to a comfortably
loud listening level and enjoy!