The first thing you should know about installing Subtext is that you don't have to install Subtext.
Subtext is a universal web app--which means ANYONE can use it.
Any device with a modern web browser can access and use Subtext. This means you can use its powerful tools for developing a story with any iPhone, any iPad, any Surface tablet, or Windows PC, or Android or Pixel and so on and so on…
One of our primary motivations for building Subtext was to make it possible for PC users and non-Mac users to have access to these powerful tools for writing WITHOUT having to buy a brand new computer.
So yes, you can use Subtext on a PC.
(Though you'll probably want to use the latest version of Chrome or Microsoft Edge, as Internet Explorer tends to be a bit behind on the times.)