Java autofill

How do I make this script that it always runs and autofills if im on the supreme website. If I press F12 and go to console and I put this in it autofill everything, but I want to make this programm so that it automatially autofills and runs if im on the site. Can somebody help me?

https://media.discordapp.net/attachments/626831176526725189/628334393429065741/unknown.png?width=507&height=675

Sorry for the late,

but what do you mean for “I want to make this programm so that it automatially autofills” ?

Do an example and be more clear please