Ping On Join is pretty straight forward, you run *ping-on-join, then press the button Toggle to enable Ping On Join, once you've done that, press Add Channel, once you mention your channel in chat and the bot deletes your message, everything is set up correctly.
To test if it works, get a friend to join your discord. If they receive a ping in the channel you can be sure it's working!
Please note that there is a ratelimit for bigger servers. The ratelimit makes sure that when a lot of people join, Tippy doesn't spam too much. This results in some users not getting pinged, which is intended.
You'll only need to worry about this when getting more than 2 join per minute. More channels will cause more users not to be pinged.