In order for your Factorio server to show in the in-game public list, you will need to get a factorio.com token.
Login/register at https://factorio.com and then navigate to the profile page.
- Copy your token by clicking "Reveal".
- Login into the control panel at https://control.low.ms
- Click Configuration Files
- Click Text Editor for Server config file (server-setting.json)
- Add your token to the `token` field.
- Enter your Factorio username into the `username` field.
- Save the file and the restart your Factorio server.