Product Key Payment Automation-Website

I need you to automate an email process for my product. When a user buys a product on my site and pays, i need an email to be sent to them automatically and a product key must be generated automatically and included in the email. If you remember, I use limelm to generate keys. There is an option to make it automatic here: [login to view URL] My website is made with [login to view URL] but the html and css and javascript and images can be edited too...it is www.justcopitbots.com. Basically, when a customer checks out and pays, they should immediately receive an email with my instructions and a working generated product key. (Ps-an email is already sent out automatically by weebly as an order conformation. I'd like to keep this, and add the key email with instructions as an additional email. Also, their email is collected during checkout. Thanks! Lmk