Hosting per client url in angular – Node application [on hold]

I am creating a web application and was deciding if I should set up a regular login page for clients or rather set up

clientname.company.com

I was wondering if there were any downsides to that and since it turns out there aren't, after reading this post on stackexchange, I am convinced I would like to set up a subdomain per client.

I am creating this web app in angular-Node-MySQL. My question is how do I set up subdomain per client thing? I would like to white label this application for clients. I am looking for just a direction. Even a very basic overview would do.