All about connecting a GPS to OpenPilot can be found in the OpenPilot wiki http://wiki.openpilot.org/display/Doc/GPS+Add-on
But be aware: If you are using a 3.3V GPS don't connect it directly to the 5V of the OpenPilot JST (FlexiPort) connector. Use a step down converter instead.
For connecting the OpenPilot with the MinimOSD you have to connect the OpenPilot JST (MainPort) with the MinimOSD as follows:
| OpenPilot JST | MinimOSD |
|---|---|
| GND | GND |
| PWR | +5V |
| TX | RX |
| RX | TX |
But be aware, that the OpenPilot is powered by max. 5V, so the output PWR from OpenPilot only carries 5V.