1. Extract the zip archive to a folder of your choice.
2. Start Gwent and go to the main menu.
3. Run injector.exe from the extracted files.
4. The tracker will now appear when ingame.
Due to the software still being under heavy development, the features are still very basic.
The following is a list of features that are already included or are currently being worked on.
The short answer is: No, you can not get banned for using this.
I asked the developers for an official statement and got this.
Meaning, it is completly safe for you to use the deck tracker.