Yes, you can write your own headings! Start by opening your Resume and clicking the Headings button (top-right of page).

You'll see the Custom Heading box beneath the Available column. Type in your desired heading and click Add Heading.  The new heading will appear at the bottom of the Assigned list. Use the up & down arrows to move it into the desired order.

Click Save, and you'll see your new heading on the resume, waiting for you to add some text!