BB Boom IZZA Notice D'utilisation page 28

For forward facing : position1,position2,position3 .
Pull the recline adjustment handle under the front seat body forward, and then
pull or push the seat forwards or backwards. Release the recline adjustment
handle in the desired position and push until you can hear a "click".
Now the child seat is locked in the desired recline position .
For rearward facing: rearward facing position
Rotate the seat body rearward facing and pull the recline adjustment handle
under the front seat body forward to the largest recline position. Release the
recline adjustment handle in the rearward facing position and push until you can
hear a "click". Now the child seat is locked in the rearward facing position .
Make sure the child seat is securely locked in the desired position by pulling or
pushing or pull on the seat body .
4.6. Height adjustment for shoulder strap and headrest
According to children's different height, the headrest and the shoulder strap can
be adjusted up and down, totally 8 positions . Adjust the headrest by pulling the
headrest adjustment handle ,raise or lower according to your child's height.
release the handle ,the headrest and the shoulder belts reach the desired height
and you will hear a "click". The harness strap should be level with your child's
shoulders. Check that the headrest is properly engaged by sliding the headrest
down a little.