Do not know exactly how to access that item from my web page, that is, when I click the button for a kit with the plugin command?

I'm not sure what you mean exactly, but there isn't any "web page" you'd be accessing as a player other than the player donating via PayPal.

my web page, which is the script for an order (I mean on my site I'm a VIP button, I click on it and I have a href command, "which I have to put in the hills to buy the last VIP address)

Still not sure what you are referring to, could you provide some specific examples of what you are referring to?