@MThun251954 In its simplest form that would be Copy a range of cells in one workbook, go to the other workbook/worksheet/cell and Paste or Paste Special (with various options).
But, perhaps you need to clarify first what you downloaded. From where? In what format? Is the data structured similarly to the data in the spreadsheet.
Best to upload example files of your spreadsheet, the downloaded file and indicate how the latter should be integrated into the first. Remove any private and confidential information before uploading, though.
