Yet for another how-to post.
How to create a background, which is a pretty important part of your blog.
First, go to your blogger home, click on your blog's title that you want to change the background too.
Next, you'll be at the overview page. Hit 'Template' in the sidebar.
This is where you'll be. Click the 'Customize' button.
In the Template Designer, click 'Background' on the sidebar.
Then click on the picture of your current background.
Now you can choose a background from one of the shown categories, or Upload your own.
Hope this helps!