You will automatically be directed to general settings, but the menu on the left provides a number of more specific settings options. The messenger platform settings are seventh on the list and have a speech bubble icon with a sideways lightning bolt on it. You must receive approval from Facebook for this form of messaging. Subscription messaging gives pages the power to send non-promotional messages to users. You’ll see this option to the right of subscription messaging. Clicking on it will open a window with a form on it. Fill out this form according to the type of page you run. You can select the type of messages you wish to send: News, Productivity, or Personal Tracking. You are then given the chance to add additional details about the messages you wish to send to users. The form also requires you to provide examples of messages you would send. Remember to make these messages non-promotional, or you will not be given access to subscription messaging. Check the box at the bottom of the form to prove that you understand. This is the blue button in the bottom right corner of the window. Once you have properly filled out the form, you will be able to submit your case for review. If your page is approved for subscription messaging, you will then be able to message users on a regular basis. Facebook says these requests can take up to five business days to process. You will receive a notification detailing Facebook’s determination.

TL;DR in Chinese:
前往Facebook主页。 单击主页右上角的设置。 在左侧的菜单中单击高级消息功能。 向下滚动至申请功能。 单击申请。 填写表单。 单击保存草稿。 单击提交审核。