is it possible to take an existing spreadsheet and upload the data in the spreadsheet so I can include it in the data on jotform?

Yes it is possible to do so, you will need the spreadsheet columns to match the column names and order of the form whose data you want to import to.

Please refer to this guide on how to do the importation

https://www.jotform.com/help/308-Import-App-Easily-import-your-Excel-or-CSV-data-into-JotForm

Let us know if you require further assistance or clarification