This tutorial for single spreadsheet document. If you want to get data from one sheet to another sheet then just follow the simple pattern given below:

‘=’ sign, sheet name, sign of exclamation mark and cell information i.e A10 (cell column name and row number)

Two examples given below for understand with good examples
01 Example if sheet name without space
=Sheet3!B2
02 Example if sheet name with space (use single code)
=’November 2016 Sale’!A2

Thanks