Google Script Authorization class

I've done my own Goolge Script, intended to run only in my own free Google Account. I need to run the script on each new google sheet copy I create from an original sheet. It works fine BUT at every new copy I need to pass the authorizing procedure again. I'd like to learn how to solve it. So the project is that someone teaches me how to authorize my own scripts only once, step by step. I've a basick knowledge. It seems to me it requires script implantation, but this process seems complex and confusing.