There is no true way to confirm friend requests. In order to "confirm" them, you have to go to their profile and click the "Add Friend" button, just like they did on yours.
This will make it so that you can see who is online and in the DC by going to your Friend's List. Also, you'll be able to see their drawings featured in the "Friends Recent Draws" section on your profile.
If you're having trouble finding the "Add Friend" button, it's located on the left side of a person's profile just to the left of the Subscribe button.
Hope that helped clear things up a bit.