After indicating in which Google Drive folder your assets are located, the platform will automatically create a Google spreadsheet so you can add/edit the asset's metadata.
See a collection spreadsheet example below:
Add a Trait Category
Every column you add after the reserved column (E) will be a trait category for your assets.
Add a Trait Value to your NFTs
After adding a trait column (on the e.g., column F 'color') you will have to add the trait value to each cell of your NFTs (e.g., cell F1 'red').
After you finish editing the spreadsheet, remember to click on the Sync button inside the collection to apply the changes.