For this tutorial, you will need:
Open a new image 150x250, 16 million colors, transparent. Set your foreground and background colors both to white.
Click on picture tube tool and select the Christmas Tree tube that you just installed. Change the scale to 50. Click in the middle of your image (75, 125) to place your Christmas Tree tube in our new image.
Duplicate your image (you should have two plain green trees). You may minimize one image until we need it later.
On one image add a new layer called "Garland". With the Garland layer active, click on your airbrush tool. Use the following settings:
Paint diagonal lines across your tree. Don't worry about going outside the area of your tree, we'll clean up the edges later. Your image should look like this:
Add another layer and call it "Bulbs". With the Bulbs layer active, click on your picture tubes tool and choose the cs-plain_circle tube that you just downloaded. (I tried using the airbrush and the paint brush, but was unable to get a "circle" - the shapes all looked square, no matter what I did. That's why I made the plain circle tube.) Change the size to 15. Now add "bulbs" randomly, avoiding the areas where you have your garland. Your image should look like this:
Make Layer1 active and using your Magic Wand tool, click anywhere outside your tree.
Make the Garland layer active and hit your delete key.
Make the Bulb layer active and hit your delete key.
Wow, you just cleaned up your image and it should look like this: