I would advice you to download a virtualizer for x86 hardware, such as VMware Player og Virtualbox (more exists, but these are the most common general purpose ones)
Then download an operating system of your choice, but Ubuntu is a popular free platform for this.
Virtualbox installing Ubuntu:
VMware Player installing Ubuntu:
This step by step tutorial should give you the general idea of how to install and run websites with .net core
Publishing an ASP.NET Core website to a cheap Linux VM host
You could start at step 0.5 (step 0, if you want to lease a VPS in stead of running a VM)
Guides might be slightly outdated, but they should give you the general idea, and point you to the right direction.
Not only does this give you what you currently want (for testing purposes) it also teaches you a great deal of knowledge that will be useful for you, if you desire to continue testing software on Linux servers.
Alternatively, you could download software to run you system directly in Windows.