You can do this using PI Builder as well. Here is a video you may find helpful, but this is easiest if you import an element and make edits to the data references of that element, and then publish the spreadsheet as a new element as shown in the video. If all of your assets can be built off of AF template, then it is possible to make the template in PI System Explorer and then create a new element using PI Builder.
Please let me know if this helps! If you have more questions, additional details on what you already have created (or not created) in AF will help.