In case Ты don't have Photoshop, Ты can download it link

Now that Ты have Photoshop, we can get started.
First Ты need to click File--->New---> width 800, height 100 pixels. Then Ты click Ok and Ты have a background.

Now Ты click File--->Open and Ты select a фото Ты want to open. Then Ты crop and resize it. I usually choose 110 или 120 height. Now right click on little window and Переместить to new window. Now your image is in new window and Ты need to drag it to your banner. Then Ты use a little Стрела from the panel on the left and Переместить your image where Ты want it.

You do...

Basically, PSD is a coloring. There are many amazing PSDs out there, which is great for people like me who are not good at coloring their stuff.
link

I'm sure that a video tutorial is much better than anything L could write here.
Here are some PSDs L like, all from Deviantart:
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