Adding alias to URL

Hi I am trying to create a stage site for testing and I would like to add “stage” to the URL. e.g. https://www.domain.com to https://www.stage-domain.com or https://www.domain.com/stage.

What is the best way of going about getting this done? Is there anyway to do it from wordpress without needed to create a new domain name maybe if I edit the conf file??

Thanks.