After building the drone, it is a good idea to first have a look at the RC transmitter and set it up correctly. A standard setup is described which should be easy and safe to use. Please have a good look at it.
Then the only thing left to do is setting up the software on the FMU. It might be necessary to first setup a bootloader, if it isn't already present on your board. Determine if you board already has a bootloader, and if not, write the bootloader to the board using the debugger.
When the bootloader is installed on the FMU, you are ready to continue with installing or upgrading the firmware and configuring the software.