How do I add a zero in front of a Number in Excel?

How do I add a zero in front of a Number in Excel?
To do this:

Select all the cells you need to add a zero to, right-click and select Format Cells.
In the Number tab, select Custom.
Under Type, enter 6 zeros.
Click OK.

To do this:
  1. Select all the cells you need to add a zero to, right-click and select Format Cells.
  2. In the Number tab, select Custom.
  3. Under Type, enter 6 zeros.
  4. Click OK.