Warning: 

Do not put the shoulder section of the seatbelt or allow the child to put the shoulder section of the seatbelt under their arm or behind
their back. Failure to follow this instruction could reduce the effectiveness of the seatbelt and increase the risk of injury or death in a crash.

Note:

For vehicles with adjustable head restraints, route the tether strap under the head restraint and between the head restraint posts, otherwise route the tether strap over the top of the seat backrest.