Subdomain and subdirectory question

My website host have a service where if I use a directory it goes automatically as subdomain.

So for example, for I can, as well, use

I'm trying now to install Multisite, but it's confusing because I am practically using subdirectories, but they're are used as subdomains, and in my WP options I use a subdomain, not a subdirectory.

What should I do about this here in this tutorial:

in the step "Setting up your sub-domains or sub-directories"?

Thank you.