Download the follow .wav file and load it into you DAW: PINK NOISE FULL bw -20 dBFS.wav
Pan the output to just the left and set a dB meter (you can find free dB meter apps for your phone) at the listening position) where you head will be relative to the speakers.
Set your audio interfaces volume to a known level (I usually set mine to -10 dB so that I can boost things that are not yet master but know that when I listen to something that has been mastered that I need to set my volume knob to -10 dB or quieter).
Play the audio file and adjust the setting on your studio monitor until you dB meter read 85 dB when set to dB-C weighting.
Repeat for the other speaker.
Sit at the listening position and pan the sound from right to left and back again confirming that the sound appears balanced between the left and right speakers.
Listen to your “reference” tracks and confirm the speakers sound as good as possible adjusting any “EQ” setting the speakers may have and rechecking that you dB meter still read 85 dB when the sound is panned to just one speaker.