Step 1 – Adjust and fix the shoulder strap
Ensure the elastic straps are not too tight; there should be a 1-finger thick breathing space after adjustment.
Step 2 – Check the cup
See that the cup fully supports the breast shape, check that the bottom rim is not too tight
Step 3 – Push the muscle
To ensure an appropriate fit, you can test by pushing your muscle. Bend to 45 degrees, put one palm thru the other underarm toward your back. Use the palm to push the muscle from the back toward the front of the chest. Raise your hand, but do not press the upper chest.