When you meet someone in 2or3 who you want to follow, you can click on the person’s profile picture to see their profile page. Then you can click on the “Follow” button to follow him/her.
If you no longer want to follow someone, simply click on “Following” to unfollow, and then confirm that you want to unfollow the person.
When another person in 2or3 follows you, you will receive a notification.
In the “You” section, you can see how many people you are following and how many followers you have.