Before proceeding, make note of your antenna position, picture quality, and signal strength, then rotate the antenna east. The picture should go to snow then reappear with less picture quality and weaker signal strength. The picture should go to snow again then re-appear on a weaker signal or a different satellite. Next, reposition the antenna to your starting position and move west repeating the procedure you did for the east. It is highly recommended that you be able to skew the polarity by remote control with a polarizer such as a Chaparral Polor-Rotor.
Shack sells an inexpensive modulator.
After Authorization, some Affiliates experience freeze framing, lockup, and color bars. Be certain your dish is large enough to collect the signal, a 3.7 meter antenna with a phase stable LNB is recommended. LED changes from green to amber to red you will need to re-adjust the dish point or polarity. This connection should be made with a 9 pin serial cable. The following example should give you an understanding of how to accomplish this.