The update should be released in a few days according to this
However, I just got the 1.9.1 update by switching to Chinese then downloading it. It works great and now my screen has a pin.
When you have the update you can set a pin under Settings > Systems > Keyguard Setting.
I took pictures of the English screen before I switched to Chinese (simplified) so that I would know how to navigate. When you get to About > Software Update tap the first option at the bottom. Then it will check and pull up the update. Tap the right button to update.
Another trick to use when in Chinese is to use Google Translate on your phone. You will be able to use the camera to instantly translate.