Here are the steps to change a Blogger theme: 

1. Sign in to your Blogger account. 

2. From the Dashboard, click on the drop-down menu next to the blog you want to change the theme for and select "Theme." 

3. On the "Theme" page, click on the "Backup / Restore" button located in the top right corner. 

4. Click on the "Download Theme" button to save a backup copy of your current theme. This is an important step in case you want to switch back to your old theme later. 

5. Browse the available themes or search for a specific keyword to find a theme that you like. 

6. Once you've found the theme you want to use, hover over it and click the "Preview" button to see what your blog would look like with that theme. 

7. If you're happy with the new theme, click the "Apply To Blog" button to activate it. That's it! Your blog should now be using the new Blogger theme.