Route groups may also be used to handle sub-domain routing. Sub-domains may be assigned route parameters just like route URIs, allowing you to capture a portion of the sub-domain for usage in your route or controller. The sub-domain may be specified by calling the the domain method before defining the group:
I used subdomains in multiple projects. It really works as simple as the documentation example states, I can only advice to read the documentation and implement the example (with your own domain obviously. What is your problem?
Don't forgot to register the subdomains somewhere to point to the same location as the regular domain so all subdomains are pointing to the same Laravel installation, this is a tiny but important detail.