1 - Login to your Blogger Dashboard. Click on "Template".
2 - Click on "Backup/Restore".
3 - Always backup your current template, before install a new template, this prevent some frustation! aff..!!
4 - OK! Now you are ready... click on "Browse".
5 - Now select your new template (important! it have to be a XML FILE) and click Open.
6 - Click on "Upload".
And That's All, I told you it is easy...START BLOGGING!! ;)
Well, I hope what that information became useful for you, it is you can comment, it's FREE!!!