When you set up a new Blogger site, you can select from among sixteen default different templates, the majority of which has more than one theme variation you can select. When I first started blogging, I often tried two or three of the default templates before I settled on one that fit the theme of my site okay. You can use one of the following methods to change your existing template.
Picking a New Blogger Default Template
After you set up your blog, you may decide that you do not like the template so much, or you might just want to give it a fresh look. There are a couple of ways you can change your template. The easiest way is to simply switch to one of the other default templates provided by Blogger. You can switch templates by going to Layout -> Pick New Template from your Blogger account dashboard. You can pick a new template as simply as you selected your initial one. All the information (posts, pictures, and videos) you have already placed on your blog will be retained. Blogger's system separates the actual information (your posts and media) presented on a blog from the way in which the information is presented – your blog's theme.
When you change your template by choosing Pick New Template, Blogger's system is intelligent enough to preserve the gadgets you currently have set up. For instance, if you have added some gadgets using the Add a Gadget link on the Layout -> Page Elements page, those gadgets will be preserved in your new template design. I'll discuss later a method for changing your template design that requires more caution.
Editing Your Template's XML Code
Another way that you can customize your template is by editing the blog's template file. You can access the template file by going to Layout -> Edit HTML. Blogger would probably be more accurate naming the link "Edit XML", since that's what you're actually editing. What you'll find in the template file are some variable definitions, some CSS style definitions, and finally the body of the blog page, which contains a bunch of XML tags that look something like this:
In order to effectively edit your template beyond simply changing fonts and colors in the variable definition section, you'll need to know (or be willing to learn) some things about CSS and the Blogger XML schema. It will likely take some studying of the existing XML setup and some experimenting to make the improvements you're looking for. As you make changes, you might want to keep a backup copy of your last working template so you do not have to go back to work from the original template file if you mess something up.
Installing a Third-party Blogger Template
The third way to change your blog's theme is to download and install a Blogger template created by a designer. There are many free Blogger templates available for download all over the Internet.
To install a third-party Blogger template, save the template XML file to your computer. Then, from the Layout -> Edit HTML page, click Browse …, and find the template file on your computer. Then click Open to return to the HTML page. Click Upload to upload the new template.
Something to keep in mind if you are using a third-party blog template is that if you have added gadgets to your blog (eg Followers, Poll, Labels, etc.), you need to be careful when using a third-party template to avoid removing those gadgets. If you download and install a template that does not support your custom gadgets, they will be deleted when the new template is saved.
If your new template does have gadget discrepancies, you will receive the following message when you click the Upload button.
Widgets are about to be deleted
Please confirm that the following widgets should be deleted. All the widgets' configuration data will be lost.
The warning message will then list those gadgets that will be deleted if you proceed with uploading the new template. To avoid losing your existing gadgets, you'll need to find the XML tags that represent those gadgets in your current template, and merge those tags into the template you want to upload. Doing so may be a little tricky. You might be able to get some help from the original template designer.
Each of these three methods of changing your existing themes has advantages and disadvantages. Hopefully this article has helped you understand the issues involved so you can make an informed decision. Happy blogging!