From the chatting list, tap the Menu icon (at the upper-right corner of the screen) > Settings.
Tap your account to access the following settings: Profile photo, Share your status, Hangouts notifications & invites, Video calls, Customize invites, Google+ profile, Phone number confirmed, Blocked people, Hidden contacts, Sign out, and Improve Hangouts.
Tap SMS to access the following settings: SMS enabled, Import SMS, Notifications, Sound, Vibrate, Group messaging, Delete old messages, Delivery reports, Auto retrieve MMS, and Roaming auto-retrieve.