Below you have the scheamtic for the transmitter. We connect the battery to the charger and we add a slide switch at the output in order to be able to totally turn off the remote. We supply Vcc to the Arduino and transmitter. The FTDI module is not part of the scheamtic, is just used to upload the code once. Connect all 4 buttons to GND on one side, and the other side connect it to pins D2 to D5. The DATA pin for the radio module goes to D12 pin for the SPI connection.