How to add verify licence to my app

Hi guys, i’m new at codecanyon i want to sell a python.exe and i want to integrate a verify code purchase to my app code source and a license key so that the buyer will run the .exe in one computer i had reading some stuff about envato api and really i didnt get it that much, any way that could i make this i’m really confused i need your help thank you !

@baileyherbert i need help please