Start Filedrop by clicking the Extensions menu-> click FileDrop-> Start FileDrop. If you don’t see it please refresh the document/page.
Select a cell in the Google Sheets and just drag and drop your file in the FileDrop upload area. Your file will be automatically uploaded to your Google Drive in the FileDrop folder.
If you want to share the files you upload with your colleagues or team select the correct permissions in the settings tab.
The FileDrop folder is created automatically when you install the add-on.
Your files will appear as “filename.ext” and it will be linked automatically to the file in Google Drive in the respective cells.
The second option is to click the Choose files button and the file explorer on your computer will open and you can search or select the files you want to upload.
Please also read
How do I add files from Google Drive
Select and insert multiple files