make a backup of your pc using tools like EaseUS Todo Backup
Download your favourite LuxOS flavour from here.
Write the iso in an empty usb flash drive (all the existing files on the usb) using Rufus.
Now we are going to install the os on the hard disk Warming: ALL YOUR FILES ON YOUR HARD DISK WILL BE PERMANENTLY DELETED. Firstly shut down the windows. After that press the power button again and immediately press F12. Your pc will show you the boot options, select LuxOS to boot in it. Then follow the guide on the screen to install it