Canon EOS M50 Mark II Advanced User's Manual page 52

2.
Attach the lens.
Align the white mount index on the lens with the mount index on the
camera and turn the lens as shown until it clicks into place.
3.
Prepare to shoot.
Press (1) as you turn (2) slightly, then release (1).
Turn (2) a little more until it clicks.
4.
Remove the front lens cap.
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