For proper installation you need to create a folder in your Worldsplayer folder named pax.

This world can be added to your teleport list by editting your worlds.ini file. 

To add it find the line MaxInstalledWorlds=   and add 1 to the number there already

next scrolldown to the end of your installed worlds list and add InstalledWorldXX=Pax and replace the XX with the number you raised your MaxInstalledWorlds to.

Now when you resart Worlds you'll find Pax at the end of your Teleport list.

Enjoy 
Pax_