If you're sure you REALLY want to do this, drag the mouse toward your icon sign at the top right, and underneath, you will see "Settings". Once you click it, see "Deactivation" on the left side, and click that. If you ACTUALLY are leaving DA, then click "Yes, I'm leaving DeviantArt"
Hey if you do that you only have 14 days till you can come back. And if that goes over the days, your account will be permanently removed and deleted.