The user manual for the shock is online here (click the "owner's manual" item and download it):
http://www.srsuntour-cycling.com/dst...+80+29%27.html
From looking at the manual (page 11) it appears that the lockout is on the right side - black knob with a little green dot (though yours looks a little different based on your pics). When the tab is rotated forward, the shock is unlocked, and when it is rotated back, it is locked.
Try it out. Twist the knob. If it is the lockout it should have two positions - essentially "off" and "on". twist it. If the knob hits an obvious stop within 1/2 turn or so in either direction, that is probably it. Try one position, push down on the bars to compress the fork. if it feels springy, the lockout is off. If it feels firm and does not want to bounce, then you are locked out.