What is a one-sentence summary of the following article?
You can adjust all of your privacy settings directly in the Facebook mobile app. You'll find this in the upper-right corner (Android), or in the lower-right corner (iOS). This will open the Settings menu for your account. On iPhone, you'll need to select "Settings" and then "Account Settings." This will open your privacy settings. You can prevent your timeline posts from appearing to anyone else, essentially turning your timeline into a private blog.  Tap "Who can see your future posts?" Select "Only Me" to hide future posts from anyone but yourself. Return to the Privacy menu and select "Limit the audience for posts you've shared with friends of friends or Public?" Tap "Limit Old Posts" and then confirm to hide all of your past posts. You can lock down your timeline so that no one else can post to it or see other posts.  Return to the "Account Settings" menu and select "Timeline and tagging." Tap "Who can post on your timeline?" and then select "Only Me." Select "Who can see what others post on your timeline?" and then select "Only Me." Each item on your profile has an individual privacy setting. You'll need to change each one to "Only Me" to hide them from viewing by anyone.  Return to the main Facebook screen and open your profile page. Tap "Add Details About You." Tap the Pencil (Edit) button next to each entry. Tap the Audience menu at the bottom of the entry and select "Only Me."

Summary:
Open the Facebook app. Tap the Menu (☰) button. Select "Account Settings." Tap "Privacy." Hide your posts and tags. Block people from posting on your timeline. Hide content on your profile.