Here is the pinout for the Pixhawk Telemetry ports. When I labelled Radio TX, this is actually the telemetry ports RX, and Radio RX is the telemetry ports TX. This is because the radio TX needs to connec to pixhawk RX, etc…
For Serial 1 (Telem 1), Serial 2 (Telem 2) and Serial 3 (GPS)
Pins: 6 = GND, 5 = RTS, 4 = CTS, 3 = RX, 2 = TX, 1 = 5V where the red wire is pin 1.
Hope that helps
Here is how to connect your minimOSD board to your pixhawk, if you buy an official minimOSD board you will not receive two DF13 cables, a 6pin cable to conenct to pixhawk, and a 5pin cable to connect to APM2.6. If you dont have the latest minimOSD then you can just buy a DF13 cable and solder it to your minimOSD board as shown below.