Blogger template can easily access and edit to modify your layout and design.getting backup is very necessary because while adding a widget we may need to edit template and if you are not very well aware of coding you can made mistake in template and only one mistake can totally change the design.
To avoid unwanted changes in you blog design.you have to get backup so that you can restore it later.you can save the file in your computer that can be upload to restore your template.
How to get backup of template
It is very easy to get backup.
First login to your blogger account
Now click on the left side template
At the top Right corner you can see backup and
restore option as you can see in image above.
click it.
New pop up appear to get back up click
download full template
Now you template file is downloaded in your computer.
keep it save.
Restore the blogger template
To restore you have to repeat the above process but now instead of
downloading template upload the xml file of template that you save recently.
Your process finish.If you have any query or problem just ask me.