To mount the lens, first align the rounded red positioning point on the lens with the red dot above the camera mount

Then turn the lens in the direction of the arrow until it stops and the lens release button pops out with a click

If your camera looks like this, with a red dot showing inside the camera mount, do not mount he lens yet. First press in the small chrome button as shown to release the stop-down slide. Then mount the lens. Leave the stop-down slide as it is.

To remove the lens, turn it in the direction of the arrow, while pressing the lens release button, until it stops