And i have tried and tried and tried many times.
Now i know how to do it already.. =)
First, click File > Open and choose the image that you want to edit.
After you opened few file of photos, use mouse to drag the file out by clicking the bar.
It becomes like this after you dragged it out.
Double click on it to change the name and unlock.
It will pop the thing out, then you type you name you want to.
After type, click Ok.
The layer's name will become as what you typed and unlocked.
Same goes to the others.
Then, Double click on the picture drag one of the picture to another file.
Click Edit > Free Transform to resize the picture and even rotate.
And remember to click Apply.
After that, right click on the layer and click merge down.
And it has become 2 in 1.
Click the eye to indicates layer visibility.
And it will become like this.
Click on Add layer mask which is vector mask.
Then will become like this.
Choose Gradient tool on optional bar.
The line will just form a while when you draw.
It will become like this.
Add new layer.
Change the name to background.
Fill the background colour with any colour you like by using Paint Bucket
by clicking the paint bucket in toolbox.
After clicking the Paint Bucket, click once the layer which visible just now.
Finally, the image with layering IS DONE !! ~
Enjoy Photoshop! =)