This covers Customizing the Quick Access Toolbar and enabling the Developer Tab for Excel 2007 onwards:
If you want to work with Macros and other Advanced features in Excel you need to show the Developer Tab and it’s also a good idea to customize the Quick Access Toolbar to give you easy access to the key tools.
There are two files on www.mathsfiles.com/Excel_Files in the techniques section that show how to do this.
Instructions pdf file
Watch a Demo (based on Excel 2007)
Note: The process is much the same for later versions of Excel but the way to show the Developer Tab is found by going to Excel Options and then the section for Customizing the Ribbon. Just check the box for the Developer Tab.