Partially pull back the slide to reveal two fingers on the base of the barrel and two grooves on the body and also, a notch in the slide.
Holding the tip of the barrel, twist it so the the fingers turn in the groove and up past the slide notch.
When barrel is free from the body, slide the slide and barrel forward off the body.
You will have three basic parts: The Slide and Barrel (which do not come apart), the Slide-spring, and the body.
Be very careful after this point! The rest of the gun, parts are very fragile and easily spring from their places. So I recommend going only to the point of freeing the barrel to clean and lube.