Your seat may differ from the one being used in this video, however the procedure is the same.

Pre-crash locking vehicle seat belts will lock in one of two places:
1) the latch plate, or
2) the retractor.
If your vehicle seat belt system does not include a pre-crash locking feature, use of the locking clip is required.

Check your vehicle owner's manual to determine how to lock your seat belt system when installing a child restraint.