referense to sheet in opened workbook

If some spreadsheet and workbook are already opened like
this:

Set xlBook = xlApp.Workbooks.Open(“BookName”)
Set xlSheet = xlBook.Worksheets(“theFirstSheetName”)
xlSheet.Activate
xlApp.Visible = True

How could I activate another theSecondSheetName
spreadsheet to be able to see it from the same workbook?

Thanks