Here is How to Install a theme on blogger
Log on to your Google Account, then sign in to your blogger
Download your theme, after downloading extract the downloaded file
After extracting the XML document, you copy it to your desktop where you can easily access it.
Go back to Blogger, then click on theme
Then click on the arrow close to CUSTOMIZE
After clicking on the arrow close to CUSTOMIZE, you click on RESTORE as shown in the image below.
then click on UPLOAD
Then you click on the XML file you copied to your desktop earlier, then click OPEN
Click on VIEW BLOG and see the changes
Smilehopego together we go