How do I follow someone? And how do I allow someone to follow me?
You can follow someone by finding them in your contacts, through Facebook, or through the suggestions in your feed. If that person's profile is set to private, they will need to accept your request to follow them.
If your profile is set to private, you will need to approve any requests you receive from people who wish to follow you. For more information on account privacy, you can read this article.