You can use the "Cash Out" link located in the top-right corner of the screen, underneath your profile photo:
If you see a "Donate" link instead of a "Cash Out" link, this means you have donations turned on. You can toggle Donations on or off on your Profile page.
Cash out requirements:
The minimum cash out amount is $2 plus Bitcoin network fees.
You must be a verified user in good standing to cash out.