define excel file on server as a worksheet? [closed]

i am trying to make a report page. there is a form in one of my pages. users add their data in this page. and when they click 'report' button after completing the form, i want them to download this excel file with their data. I want to learn how to define this excel file as a beginning worksheet

        ExcelPackage excelN = new ExcelPackage();

        System.Data.DataTable dt = processedOrders;

        byte[] fileBytes = File.ReadAllBytes(Server.MapPath("~/Files/form.xls"));

        var workSheet = excelN.Workbook.Worksheets.Add(fileBytes.ToString());