Remove the top drawer of the dresser and measure the width of the dresser. Divide the width into thirds and mark two points with a pencil between the thirds. For example, if the dresser is 30 inches wide, place pencil marks at the 10- and 20-inch lines.
Position the dresser firmly against the wall and drill through the two pencil marks. Drill deeply enough that your drill bit goes through the dresser and the wall.
Unwind the toggle off each toggle bolt and thread an appropriate-sized washer on each bolt. Screw the toggles back into place, making sure they're close to the ends of their bolts.
Slide the toggle bolts, one at a time, through the holes in the dresser and drywall. Use a screwdriver to tighten the head on each bolt until it is firm against the wall. The toggles on each bolt will dig slightly into the backside of the drywall, pulling the dresser tight against the wall.