When viewing a friend's post, scroll to the final photo in the post, then click the R button. This will launch the voice comments screen. Hold the ✓ button to record your voice comment. Press the ✓ button again to post the comment or press L+R simultaneously to erase the recording. Listen to your friends' voice comments by scrolling through the voice comments list using L/R buttons, and pressing select on the comment you'd like to listen to. Press L+R simultaneously to return to the photo gallery.