First, you should have a blog. When you create a blog, you will be asked to choose a template. Just choose any one of them. You'll be able to customize it a lot later.
Now when you're on Blogger.com, you'll see a list of your blogs. To the right of the name of your blog, click on the little downward pointing arrow. Click on "Template."
You'll see a picture of your blog, with the words "Live On Blog." Click on "Customize" underneath the picture.
If you want to find a good background for your blog, you can use the ones offered by Blogger. On the left side of the screen, under the word "Template," click "Background."
You'll see a picture of the background your blog came with. There is a little downward pointing arrow next to it Click it. Here you will see all sorts of already-made backgrounds. Click on the different category names to see more backgrounds. If you want to choose one of these, just click on it, then click the orange "Done" button.
If you'd rather choose your own background, instead of choosing a picture under one of the categories, click "Upload images." Then, you can choose a picture you've saved on your computer.
I find pictures to use by Googling "free _____ Wallpaper." For instance, to find my Thanksgiving background, I searched for "Free Thanksgiving Wallpaper." I chose an image, saved it to my computer, and uploaded it.
Once you'e uploaded an image, you should see the word "Background Image" over a picture of your new background image. To the right of this, you'll see two drop-down lists. One says "Alignment." Just leave it alone. The next one gives you the choices of "Don't tile" or "Tile." Choose tile. I also like to check "scroll with page."
|This is what the Template Designer will look like on Blogger.|
If you scroll down, you should be able to preview how the new background looks on your blog.
You can also click on the "Advanced" tab (under the Template list) and get options to change the fonts and colors for all the different sections of the blog. That part is always fun for me.
Don't forget to go to the upper right hand corner of the screen and click "Apply to blog!"
I hope that helped! Let me know if you have any other questions!