I just have to use the desktop app and put the files on my server.
Not exactly... Showkase is not a desktop application. Showkase is installed and run on the server itself (in a web browser interface) and, as such, all Showkase pages are created directly on the server so there's nothing to transfer to the server (other than the initial installation files).
Here are the Installation Instructions.
It's certainly very easy to install and start using Showkase. Check out the link above and the Getting Started guide below the Installation Instructions.
It'll probably take you longer to set up your web server that it will to install Showkase.
Showkase requires PHP (minimum version PHP 5.2.0) so you'll need to install that as well as Apache HTTP Server.
Please use a version of PHP between 5.2.0 and 8.1.16. There's currently an issue with Showkase under PHP 8.2 (due to a deprecated PHP function) which I have notified the developers about. This should be addressed for the next release but, in the meantime, just use PHP 8.1.16 (the latest version in the PHP 8.1 branch) and you should be fine.
I don't know exactly how much time you might need to spend configuring Apache/PHP as I've never set up a home web server before. Most commercial web servers are set up with PHP ready to go and configured to give users the least amount of trouble.
After setting up your web server but before installing Showkase, I'd recommend installing and running the Showkase Server Compatibility Test to make sure that your web server has all the basic functionality that Showkase needs. Here are the basic requirements:
Further information can be found in the link above.
I hope this helps to get you started.