First make sure you're looking at the AdBlock menu in Chrome. MyAdBlock is not yet available in Firefox, Microsoft Edge, or Safari.
If you're a Chrome user, please stay tuned. MyAdBlock is a brand-new product. We're keeping it in limited release until we're certain everything is working the way we want it to. Please watch Facebook, Twitter, and AdBlock's Blog for an announcement when MyAdBlock is available for all our Chrome fans.