Start by placing the medium-sized tips in your ears. Grab your left earlobe with your right hand and pull the lobe downwards to widen your ear canal. Then, use your left index finger to gently push the tip further into your ear until you feel the seal. Let go of your earlobe and you should feel the seal tighten. Now do the same for your right ear.
If the medium tips do not create a seal, try with the small tips and finally the large ones. The most important thing for the performance of Here is to get a good seal.