How does the new hangouts app work?

I'm new to Android, and I just downloaded the update that removed Google Talk and replaced it with the Hangouts app. I only do instant messaging, and I only talk to people who are online, so seeing who's online, who's away, and who's busy is important to me. The Google Talk app sorted my contacts so that people who were online were on the top. The Hangouts app isn't doing this as far as I can tell--I'm just getting a huge list of everyone. I don't see an option to sort the list. What am I missing? I'm sure it's something obvious but I'm really frustrated. Thanks for any help you can offer!