Installing XML Template on a Blogspot/Blogger Blog is quite easy. Just follow these easy steps-
1. Login to your blogger's dashboard.
2. Then go to blog's Template.
3. Click on top-right corner button Backup/Restore.
4. A new window open.
5. You might need to backup the template before you upload it, Click “download full template', to save the template file into the computer.
6. You can see the word 'Upload a template from a file on your hard drive.',
(a) Unzip the downloaded zip file.
(b) choose the '(template name).xml' file and click the button 'Upload'.
7. That's all enjoy it! :-)