1. Unplug the WHP Base Unit, fold the antenna down, then turn the device over.
    device 612/252948.jpg
  2. Gently press down on the raised arrow on the back-up battery cover, then slide it in the direction the arrow is pointing.
    device 612/252944.jpg
  3. Pull the three-prong connector out of its port and remove the back-up battery.
    device 612/252945.jpg
  4. Take the SIM card and insert it into the SIM slot, with the notch in the upper left corner and the gold contacts facing down. Slide the SIM card in until it clicks into place.
    device 612/252946.jpg
  5. If the SIM card is missing, or present but the signal strength LED still flashes red, contact AT&T Customer Care to obtain a replacement SIM card.
    device 612/252947.jpg