I went through the process of installing all the bits mentioned here (had to get a windows laptop in the end to use it).
The instructions on the blinky page might be for the full programmer rather than the “USB” version.
The instructions on the forum post were close, but I simply had to change the pin from a 6 to a 5 in:
#define UART2_TX_PIN GPIO_PIN_5
Edit/Addition: Adding serial communication
I wanted to get feedback via the serial port, but it seemed to just output the default message about the address of the device. I eventually found that the serial port could be enabled by modifying line 163 in da1458x_config_basic.h, which I wasn’t expecting as I’m using a da14531. Anyway, replace the line: