Here are some really simple steps to lock your profile on Facebook using an Android phone:
- Open the Facebook app on an Android device to enter your profile.
- Tap the three-dot menu (⋮) next to your profile picture.
- Select "Lock Profile" from the menu.
- Click the button "Lock Your Profile" for confirmation.
Your profile remains invisible to every other person except for your Facebook friends. The profile seems much less phenomenally empty to any person who is not a friend through Facebook.