I don't see a corresponding marketplace item from Roll20, so I am assuming these are digital assets you procured from somewhere else? If so, that set of digital assets can't be used as a unified, classic "Roll20 Add-On" -- where you can just update your game. You can add digital assets (images, maps, token art, PDFs) to your library... so the answer to *how* you would go about utilizing your digital assets would come down to what they are. Can you be more specific about what you have in the way of files? (What they are in terms of game objects, and also what file format they are in.)  Secondarily, scripts can be installed from your "Mod (API) Scripts" link under Settings on your game's landing page. If it's a script you can get from the Roll20 one-click, you can choose it from the dropdown and then choose "Install." If, instead, you have code that you've copied from somewhere else, first make sure that it was intended for Roll20. Different VTT platforms might all use javascript for the basic code, but they all have peculiarities of accessing and handling data/events. Code written for another platform likely won't work on Roll20. That said, if it is Roll20-friendly code, you can install it from the same "Mod (API) Scripts" page by clicking on "New Script", giving your script a unique name (unique within the scripts you already have installed), pasting the code into the window, and clicking "Save".  Utilizing the script in the game will likely be a matter of sending messages that bear the proper syntax... but what that syntax is would be up to the original author of the script to have communicated to you (either by posting somewhere or by an output to the chat panel in your game).