[The guide is not complete, is more kind of a guideline]

Gather the PCB and solder on it the various headers and the bluetooth model. Be sure to use the 3.3V version of the Arduino pro mini. You can either solder the Arduino on the board or place a header to make it detachable.

Customize the firmware

At the beginning of the sketch there are a bunch of #define lines that allow you to configure many parameters, the most important of which are the ones regarding the bluetooth communication (and they have to mach with the receiver's parameters).

[Will add a detailed description some day]

Flash the firmware on the Arduino

On this board you obviously need to flash the TX.ino firmware (found in the files tab). You can use the programming header available on the PCB. For general instructions on how to flash an Arduino pro mini look here.

Note that you need to remove the RX and TX jumpers before flashing, otherwise the bt module will interfere with the communication and you'll get not in sinc error.

[I'll upload a pinout of the board as soon as I can]