I would recommend you to use the OfficeOpenXML library provided by Microsoft and it will make your life easier.
1) Open the workbook.
2) Select the worksheet.
3) Give the range of cells. (sheet.Cells(fromrow,fromcol,torow,tocol))
4) GetCellValue method for the selected range. Now you have all the values for the given range.
5) Use your logic to export it to SQL.