I haven't seen a step by step guide. The steps to follow are to download and install the Arduino IDE from arduino.cc; start the IDE; download the software, called a sketch, from this forum; open the sketch in the IDE; connect your Arduino (in your antenna analyzer) to your computer via USB; set up the Arduino board as an Arduino Leonardo (at least that is what worked for the board I purchased); set the COM port for where your Arduino is connected; upload the software to the Arduino.
It's been a while since I started this so perhaps I forgot a step and someone else can clarify.
Here is a good explanation: https://www.arduino.cc/en/Guide/ArduinoLeonardoMicro
Uploading Code to the Leonardo, Leonardo ETH and Micro
In general, you upload code to the Leonardo or Micro as you would with the Uno or other Arduino boards. Click the upload button in the Arduino IDE and your sketch will be automatically uploaded onto the board and then started. This works more or less the same way as with the Uno: the Arduino software initiates a reset of the board, launching the bootloader - which is responsible for receiving, storing, and starting the new sketch.
However, because the serial port is virtual, it disappears when the board resets, the Arduino software uses a different strategy for timing the upload than with the Uno and other boards. In particular, after initiating the auto-reset of the Leonardo, Leonardo ETH or Micro (using the serial port selected in the Tools > Serial Port menu), the Arduino software waits for a new virtual (CDC) serial / COM port to appear - one that it assumes represents the bootloader. It then performs the upload on this newly-appeared port.
These differences affect the way you use the physical reset button to perform an upload if the auto-reset isn't working. Press and hold the reset button on the Leonardo or Micro, then hit the upload button in the Arduino software. Only release the reset button after you see the message "Uploading..." appear in the software's status bar. When you do so, the bootloader will start, creating a new virtual (CDC) serial port on the computer. The software will see that port appear and perform the upload using it. Again, this is only necessary if the normal upload process (i.e. just pressing the uploading button) doesn't work. (Note that the auto-reset is initiated when the computer opens the serial port at 1200 baud and then closes it; this won't work if something interferes with the board's USB communication - e.g. disabling interrupts.)