The anchor points (loops) are located on the top of the rear seatback. Please read the owners manual to ensure you are fitting in accordance with the manual.
Upper Tether Pathways:
Remove headrests prior to fitment to ensure a clear pathway
Passenger and Driver side upper tethers pass through loops under the headrest, directly behind the child seat and then attach to the top tether anchor loop at the rear center seating position.
Rear center seating position's upper tether strap passes through the center tether anchor loop and then attaches to either outboard anchor loop.
While fitting three seats is possible in the Navara, it is not easy to accomplish and the upper tether's begin to look messy. It's best to fit the center rear first, followed by the outer seats - ensuring you keep the straps as untwisted and cleanly through as possible