How to Upload/Change a Template of Blogger Blogs

Many newbies have problem starting a blog, one of the most common question is "how to change template of a blog".
There
are many free templates that has been shared on blogosphere, but how
will you change your current template with the one that you get from
other sites?
The second topic is about how will you make a backup of your current template?

Here you can find a lot of templates to