For the Nerf Rival Curveshot Sideswipe How do I shoot the gun?

Hello so my little brother got an Nerf Rival Curveshot Sideswide Gun yesterday for Easter. So At first i didn’t know how to shoot it because he had put in 8 balls but i watched an tutorial for the gun and i found out you need 4 balls so i took 7 of them out, but the last 1 got stuck in the shooting space and i had to disassembled the ball and i got all of the pieces out. I tried to shoot the gun using only 1 ball and it did not shoot. I tried to lock and unlock the trigger lock, to pull the priming bolt back and then forward while pressing the small black button under the priming bolt on the back. Nothing worked. How do i actually shoot the gun! Please i need to know otherwise my brother is just going to keep annoying me. Thank you!