The first step in creating a WordPress Seed Site, is to create an ordinary default WordPress site using the method provided by your host.
I don't provide guidance on how to do this as each host has its own method. Most good hosts tend to make it very easy to install WordPress, often at the click of a button. As I've already explained I will be using a sub-domain to create my Seed Site.
Consult your hosting provider to find out how to install WordPress.
Once you've created your default WordPress site, login to the admin dashboard.
Next go to dashboard → screen options (you'll find screen options is a tab at the top right of the page). Once there, uncheck the following options to declutter your dashboard.
Close the screen options tab.