Perhaps, I do not really understand your question. If you can get the values out of the Excel sheet, then what exactly is your issue hooking them up to your Windows Form? You would simply pass the result of GetCellValue to the text box or wherever you are displaying it. If this is not sufficient, please provide a little more detail about what you are looking for.
You want to view the Data from excel file in windows form ? or you want to add new records to excel sheet through Windows forms so that it should insert as new entry/row into excel file.? or you want to map & see the whole data one by one record & edit from Windows form so that it should update in the excel file when you click on submit.?-If this is the case you can use GetTable & directly map it with Gridview & you can edit from Windows form or otherwise you can also write OleDb query to fetch & append or change data.
You are using the ExportData method which returns a DataTable. If you want to get specific cell values just use the GetCellValue method. It takes in the cell letter and number (A1 for example) and returns the value of that cell. Since your Windows Form has three text boxes on it, I would assume you only need three cells from your spreadsheet.