Thanks for writing in!
I am not sure exactly which link you are talking about. It's really so simple to install a theme in the localhost.
Just go to Dashboard -> Appearance -> Themes then click on Add New button.
Then Click on Upload Theme and Browse the zip file and Install.
Before that please check your folder writing permission.
If that doesn't help. Please unzip the theme folder and place it inside
wp-content -> themes folder of your WordPress installation.
Then go to Dashboard -> Appearance -> themes and you will see the theme, please click on the active button.
Please check this article for more info.
This for Product validation
Hope this helps!