These instructions are for Word 2013. With notes for differences in Word 2010 and Word 2007.
1. Select File > Options
Note: Word 2010: Instruction is correct, but will looks a little bit different.
Word 2007: click the Word Start button, and select Word Options next to Exit.
2. Select Customize Ribbon
Note: Word 2010: as for 2013
Word 2007: Select the General tab (if not General, an option at the start) and select the "Show Developer tab" checkbox.