How do I assemble the Graco booster seat?

Start by inserting the armrests into the base until the buttons snap into the slots (Step 1). Select the desired armrest height and insert the height adjustment screws, then tighten them (Step 2). For models with a back support, flip the head and lower back support over, squeeze the red adjustment button to snap the pieces together, attach the elastic strap to the metal hook, and then attach the backrest to the base using the U-shaped hooks that interlock with the bars (Steps 6-11). Your booster seat will then be ready to use.