How to add friends in this forum?

Go to a person's profile page by clicking on their name in the header of a post. On their profile page, under their avatar, you'll note a column of buttons. One of them is to follow or unfollow someone.

All the people you've chosen to "follow" will appear on your profile page in the form of their avatar. Conversely, all the people who are "following" you, also appear on your profile page.

You can see examples of this in this tutorial:

http://able2know.org/topic/152761-1#post-4167402

When you wish to view the posting activity of people you are following, use the My Friends tab at the top of the page to list all their recent posts.

We do not add friends but we can follow people.

Oops, I was wrong. I have no idea.

You were right.

you can keep track of the people you follow in the My Friends tab at the top of each page...