INSTALL INSTRUCTIONS: This is a very convenient method for installing all M2TW mods, not just mine.
1) Make a copy the "Launcher.exe" from your M2TW folder and rename it "kingdoms" (if you already have a "kingdoms" you should be fine).
2) Put the Petty_Kings folder into your mods directory and DO NOT CHANGE THE FOLDER'S NAME.
Assuming you have the "kingdoms.exe" and the correctly named "Petty_Kings" then you can simply double-click on AOPK.bat in the Petty_Kings folder and it will launch the mod.
(Alternatively if this doesn't work you can use a custom launcher or just rename the folder "americas" and launch that campaign)