Hi, when you want someone to follow you, click on the "Message" button that appears next to the Follow/Unfollow button. Then this message will appear: "Please write a quick introduction to yourself. Let this person know how you can help them with your native language, and how you're interested in their language and culture!
Once this person follows you, you'll be able to send direct messages and chat"
Click 'Send' and you will be sending a follower request NOT a message. You can then message them.