Well, there is a couple of ways to do this. THe first way is to create an object reference to sheet 1 (or sheet 2 etc.). The other way is to just use the index references for the sheet. For example
Note - you dont need to select the sheet to put values into a cell.
Public Sub test()
Dim Sheet2 As Sheets
'create object reference to sheet 2
Set Sheets2 = Worksheets(2)
'Set Sheets2 = Worksheets("Sheet2") would also work
Sheets2.Select 'you dont need to select the sheet
Sheets2.Range("A1").Value = "Test"
'or this - refer to sheets number 2.
Sheets(2).Range("A1").Value = "Test"