Tutorials:

Concept 1: Spreadsheets do math, they add, subtract, multiply and divide.

Concept 2: Spreadsheets can use words too.

Concept 3: Spreadsheets can perform math functions automatically by using formulas.

Concept 4: Spreadsheets can make graphs and charts.

Spreadsheets are made up of cells.  
The columns across the top are letters, the rows down the side are numbers.  
Cells are referred to by the letter followed by the number, ex: A1, C4.

The Basics:

1. Cells can be resized - Format Menu>Row Height or Column Width

Select the cells you want to act on by clicking and dragging on them.

2. Cells can have text - Click in the cell and type, your words will appear in a box like the one below which will be above the cell grid.

3. Cells can have raw data or numbers - Click in the cell and type, your numbers will appear in the formula box l

4. Cells can have formulas, formulas start with an equals sign.   Here are some examples

=SUM(B3:K3) This would add the numbers in cell B3 through cell K3.

=(B3+C3+D3+E3+F3+G3+H3+I3+J3+K3) This would do the same thing.

=(L3/10))   This would take the total in Cell L3 and divide it by 10, the slash is division.

=(E2*E3) This would multiply the number in cell E2 times the number in E3)

+ = addition

- = subtraction

/ = division

* = multiplication

Advanced :   If you have a formula in one cell and you want the same formula in all the cells below it, but you want it to change relative to the cell location, do this: Click in the cell that has the formula and drag across the cells you want to add the formula to, release.   Click on the Edit Menu , drag down to Fill , and choose Across or Down , depending on where you want it to go.

You can also format the numbers in a cell to show currency, percentages, decimal places, etc... Click and drag on the cells you want to work on, release, click on the Format Menu, drag to Cells and investigate the next window's options.