If you are trying to add a specific to PixInsight, you can do so by going to Resources > Updates > Manage Repositories and clicking Add to paste the URL.
In the Screen Transfer Function (STF) , the button (represented by a small chain icon in the top left of the STF window) determines how PixInsight calculates an automatic stretch for your image. pixinsight lerar link
You paste the developer's URL here so PixInsight can download and update the tools automatically. Which one should you use? script repository If you are trying to add