To install Classic Blog you can do so in one of two ways:
1. The Simple, No Brainer, Piece of Cake Way:
Upload the provided classic-blog.zip file via the WordPress Admin Panel. To do so, go to “Appearance” > “Themes” in the menu, then select the “Install Themes” tab at the top of the page. Once you are on this page, select “Upload,” then “Choose File” to locate the .zip folder on your computer. After doing so, select “Install Now.”
2. The Roll Up Your Sleeves and Use a Little Elbow Grease Method:
Uncompress the provided classic-blog.zip file and upload the template contents to the /wp-content/ themes/ directory of your WordPress installation via your chosen FTP client.
Neither method has an advantage over the other, it is simply a matter of preference.
Follow the same instructions above to install the Classic Blog Plus Premium theme, but download the classic-blog-plus.zip file instead of the previous zip file.