So your new blog site is up and running and you have been happily blogging away, the thing is you’re still on the same boring template you started with. You can bet your bottom dollar if you are sick of looking at this unexciting page, your readers will be too.
Customizing your blog theme is a lot easier than many people think, and some make fundamental mistakes, while uploading a banner for example, and give up the task thinking it is too difficult.
Login into your account, go to Dashboard->Appearance->Themes and choose a theme. If there are a few weird things going on, they will be easily fixed if you know where to look.
If you need more customization check: Dashboard->Appearance->Custom CSS
and finally Dashboard->Appearance->Background image.