Identify the earbud for the left ear and the one for the right, as indicated by your product instructions. They are marked in some manner, including text, initials or colors. This distinction is important to ensure correct stereo imaging, and correct fit for each ear canal.
Connect the plug end of the earbuds into the music device's output jack, and adjust the sound to a medium low volume.
Insert the earbuds into the correct ears, applying enough pressure for the earbud to stay in place but not too much as to distort sound or harm your ears. Adjust as necessary to get the optimum placement.