This config goes in a hidden folder in your linux user's home folder called .thelounge
It is created automatically when you first run The Lounge as the linux user which you can do from the Desktop script called loungestart.sh
Once it exists copy config.js to ~/.thelounge

You will need to create a Lounge user.  Here are some commands you can run from the Linux terminal

You can start The Lounge with this command
THELOUNGE_HOME="$HOME/.thelounge" thelounge start

Add a user with this command
THELOUNGE_HOME="$HOME/.thelounge" thelounge add

If it complains that there is no users folder run mkdir ~/.thelounge/users

Reset a Lounge user's pass with this command
THELOUNGE_HOME="$HOME/.thelounge" thelounge reset Joe

Note that on the Desktop I have also provided a script to stop The Lounge.  If your Lounge is managed by systemd the loungestop.sh script will not work.
Instead you can use sudo systemctl stop thelounge