Push the pin out of the original hinge and swap it with the 3d printed one.
Unscrew the sma adapter.
The counterpart needs to be glued to the inside from inside of the radio to the outer bracket.
There is no end stop due to the limited space so do not turn too far.
Be very careful with the ufl connector! I've ripped mine off.
https://www.radiomasterrc.com/products/pocket-replacement-antenna-assembly
The author marked this model as their own original creation.