Here are the steps to making one cell display the information in another cell. When the source cell is changed, the cell that refers to it will change as well:
1) Click on the cell that will refer to another cell
2) Type the equals sign in the formula bar.
3) Click on the source cell
4) Hit Enter
The cell that refers to the source cell will have one of the following formulas, depending on whether the two cells are on the same spreadsheet or different spreadsheets:
Same sheet example: =A1 (this would refer to the cell in column A and row 1)
Different sheet example: =Sheet2!A1 (this would refer to a cell in column A and row 1 of Sheet2.