Hi jackman,
Have you initialized the anchor already? I believe the anchor has to be initialized with a position and added to a network along with the tag for them to communicate with each other. This is easily done in the DRTLS Manager Android app.
The Python code here can be run on the Raspberry Pi or your PC with the tag connected through USB like you are doing. Just save to a file and run with python3 filename.py.
You can see this documentation on how to use serial with Python:
https://pyserial.readthedocs.io/en/latest/shortintro.html