When in your dashboard, go down and click on Appearance and when the window opens you will see it as the last option. Also if the appearance has already been clicked you will see the editor in the left side menu.
You should see Appearance highlighted in Blue – that’s the section title
Then you will see 5 options in the appearance window
* Theme Options
However, unless you are some what familiar with php, css and html, I recommend you stay out of the Editor. You run the risk of losing your whole website if you screw something up.