I do not understand how to Validate my Domain

I do not understand how to "validate" my domain.

I selected our domain name (our wed page address) waterforhumans dot org

Is this the domain I should use?

Your help message states to make an HTML file and upload it.

I do not understand how to do this. I do not have an html editor. Can you please clarify and provide a method to verify my domain for a non tech guy?

Thanks
Rick