To share with friends you first need to record a video, to do this hold your arm out at a 45o
angle (Like you would for the kinect guide) which brings up a pause screen, select 'Record Video' from here and record your 15second video.
Once the video has been recorded you will be asked if you want to share, press yes and yes again to 'Share with Friends' and the achievement will pop once the upload is complete.
You will also unlock Global Hero in Kinect Fun Labs: I Am Super!
by sharing with friends.