Simply click the red link on the HOME page. If you disabled your profile yourself, and everything was fine, your profile will re-enable. If your profile was disabled because it did not meet the minimum nudity requirement, clicking the link will take you to the pic upload page. If you don't have a shirt off pic, you'll need to upload one (scroll down). If you do have a shirt off pic, it's probably incorrectly labelled. The 'what's visible' section needs to be marked 'body clothes off' on the correct pic (and then click update). Once the label has been corrected, scroll back to the top of the page and you will see the enable option (click it).
It's very important that each pic is correctly labelled. Do not add the clothes off label to the wrong pic. This is checked, and will result in your profile getting disabled again.