To use conditional formatting, select a range of data that you want to apply the formatting to.

Then click on the Format menu in the menu bar and choose Conditional Formatting from the list of options.

This will display the conditional formatting dialogue box.

You can now enter rules or conditions that have to be met for the different formatting to occur.

The goal here is to enter values in the text fields to build conditions using the operators in the drop down list. For example, you could select equal to from the list, and then enter the value 425 in the field provided. The condition would now be Cell value = 425. You can then click the Format button to set properties like font size, background shading, or font colour.

When you are finished, you can see the new format in the preview area provided. If the condition you specified is true (cell value =425) for any values in the selected range, the cells containing those values will be reformatted.

Since there is a cell value in the selected range that makes the condition true, the conditional formatting is applied to the cell.

You can apply multiple conditions to a group of cells, by clicking the Add button on the bottom of the Conditional Formatting dialogue box. You can also specify conditions based on formulas, by choosing Formula Is rather than Cell Value Is from the list in the upper left of the dialogue box.