The Endless OS Installer for Windows is a utility that runs under Microsoft Windows. It lets you conveniently evaluate and install Endless OS, either directly on your PC or by creating a Endless USB Stick which can be used for these purposes.
To proceed, please refer to the documentation which matches what you are trying to do:
Create Endless USB Stick
This document explains how to turn a USB storage device (e.g. thumb drive) into a bootable Endless OS Stick which can then be used to install or evaluate Endless OS on any number of computers.
Dual Boot Endless OS with Windows
This document explains how to install Endless OS alongside your existing Windows installation. When you turn your PC on, you will be presented with a menu that lets you choose between Endless OS and Windows.
Further details are provided in the documentation collected below.