⬢Place all three parts in front of you. Note both "arms" are identical. Make sure the C shaped opening, which will snap on the printer's frame is facing you.
⬢Take the "arm" on the right side, insert it gently into the main part and rotate it clockwise. It should take about half the turn to lock the part in place.
⬢Take the other "arm" on the left side, insert it gently into the main part and rotate it anti-clockwise until it locks in place.