You can run Endless OS within your existing OS by running it as a virtual machine. The instructions below show how to use VirtualBox to achieve this.
Download any Endless OS ISOs from the download page.
Step 1. Create an empty VM in Virtualbox
Click on 'Create'
Step 2. Boot into Live image:
Step 3. Doubleclick on the just create VM to install Endless OS into your virtual disk.