Either clone this repository, or download it as a zip, then unzip it.
Once you've done that, you can cd into the directory, and run the following command:
pynetworktables2js --team 846
A server will start up, and you can visit the dashboard at http://localhost:8888.
You may find it convenient to create a bat file with the following contents
cd %PATH_TO_dashboard_DIR%
start "" http://localhost:8888
pynetworktables2js --team 846
Double clicking it will do all of the above for you (except downloading this repository).
Note that the included pynetworktables2js executable is a special version built from a version that supports backups and Infinity and NaN values. Here is the repository if you're interested. Without the special executable, you cannot download/restore backups.