BB Boom IZZA Notice D'utilisation page 26

4.2. Checking the shoulder strap height
NO -Too low
Always check that the shoulder straps are at the same correct height for your
child. The child's shoulders should always be thread through the slots in the
cover and seat shell that are closest to the top of your child's shoulders.
4.3. Usage of buckle
Firstly ,adjust the shoulder straps height ,please proceed as follows:
Step1. Put the two metal sections of the buckle connector together.
Step2. Slot the two buckle connectors into the slot in the buckle until they "click"
in place.
Step3. Check the harness is correctly locked by pulling the shoulder straps
upwards.
To release the harness ,you can press the red button of the buckle downwards,
the two metal sections will be pop up .
NO-Too high Yes- Correct