Yes, you definitely have to manually unzip the sliding-door theme folder and then you have to upload that them to your domain.
Here’s one of my blogs on my domain that utilizes the sliding-door theme.
(I had to do some heavy tweaking)
https://www.lw-concepts.com/lw
The theme won’t show up until you’ve added the sliding-door folder inside the ‘theme’ folder located in your wp-content folder on ftp.
So once you’ve downloaded, do these steps.
Upload to domain’s ftp> look for wp-content folder> then ‘theme’ folder > then dump the contents and go back to your dashboard to see the results and activate the ‘theme’
–wolfie