You can attach files to a cell or range of cells from the attachment panel.
Attaching a File to a Cell
Select a cell or range of cells to attach the file to, then click Upload File in the Attachments panel to choose a file. You can also create a placeholder where a file should be uploaded.
After you've uploaded an attachment or created a placeholder, you can create a reference to that attachment or placeholder by selecting another cell or range of cells and choosing Add Reference from the drop-down menu.
Modifying an Attachment
You can rename attachments, replace attachments, download individual attachments, revert an attachment reference to a placeholder, or delete an attachment from the drop-down menu.
If you'd like to download all attachments on a spreadsheet, you can click Download All Attachments to download a .zip file containing all attachments on the spreadsheet.