Alright first step is to get the actual template file.I would recommend checking this site out and picking one.

After you've downloaded the template to your computer extract it somewhere I used my desktop

Then login to your Blogger Dashboard and navigate to your blog.
Navigate to the template section and click Backup/Restore.
A new window swill pop up.Click Choose File and navigate to the folder containing your template.
Now select the XML file and upload it.In my case it was funkyzine.xml it should look something like this:
Confirm it and you're all done.