Every user has a blue follow button on their profile. Use this button to follow that user. When you follow another user, any image they create will show in your stream.
To follow the creator of a great image you’ve found, click on their profile icon right about the left upper corner of the image. That will take you to their profile.
If you want to follow a specific friend, have them send you the link to their profile outside of ThingLink. You can use the search bar but there may be many people with their same name on ThingLink, or their username may be something other than their legal name.
To unfollow a user, go back to their profile and click the unfollow button where the follow button once was.
You can see who you follow and who follows you on your own profile.