Just follow these simple step-by-step instructions to install your desired Blogger template.
Step 1: After you had downloaded your desired template into your computer, unzip the file.
Step 2: Log into your Blogger Dashboard.
Step 3: Click

click to enlarge
on the Design Tab.
Step 4: Click on Edit HTML.
Step 5: You may want to backup your original template first, just in case things do not work out and you may want to revert to the old template to start over. Under Backup/Restore Template, there is a function where you can save a copy of it. Click on Download Full Template, and save it to your computer.
Step 6: Now you are all ready to upload a new template from a file on your hard drive. Click Browse and look for the template in xml format.
Step 7: Select the xml template and click Upload.
After you had uploaded the xml template, you will see that html in the box under Edit Template, had been automatically replaced with the html codes of the new template.
You may also find a message saying that says "Warning: Your new template does not include the following widgets". Select "Keep Widgets". You may click on Preview, to see how the new template looks like without losing the changes.
Once you are satisfied, click Save Template. And you are done! Your blog now has a nice new design.