It seems that right now the only profile with access to Social Features is the main one.
You can only change things like 'Interests' for a Profiel and what content the profile has access to. To do that do the following:
1) Go to your home page
2) Tap on the top left where your profile name is listed. You can also slide down.
In either case it'll show you a list of profiles.
Below that will be an 'Edit Profiles' button. Tap that.
3) Now, for each profile you'll see 'Edit' option. Tap on the profile you want to edit.
You'll get a menu with various options - choose 'Manage Content' or 'Change Interests'.
I'm guessing that at some later point of time the ability to add 'Social abilities' for Profiles will be added. But right now only the main profile can add social stuff.