For adding an asset, only the #define ADD_ASSET "Copper" line must be uncommented. The rest of the #defines can be commented out - or not, it doesn't matter.
"Comment in" or "Uncomment" means activating a line by removing its comment slashes. But before you do anything, make yourself familiar with writing and editing scripts, otherwise it's difficult to follow the descriptions in the manual. Especially you should understand what the Download script does and why you have to uncomment that line. So, before adding any asset, go through the tutorial, at least the first chapters.
For anything you do with Zorro you'll need a script. Without the ability to write scripts, adding an asset makes no sense anyway because you won't have a script that could use that asset.