How to reverse channels on spektrum transmitter

[Battery800]

so my dxe is at the service center being repaired right now, and in the meantime I have this little simple 4 channels radio from an rtf vapor box. It has 4 channels, from buttons, and nothing else. Does anyone know how to reverse the channels?

 

[MooreRC]

In the beginning of this video it might be what your looking for.