Setting up Milo with a wired connection allows you to have two separate networks for employees and for guests. If you connect Milo to your existing router, you can keep the resulting Milo network for your customers only, and just continue using your existing router network for your employees.
After you've connected the Milo base to your router during setup, you will find the default Milo network in your device's wifi network options, in addition to your existing network. The default network name and password can be found on the bottom of the base. You can then connect to this network and change its name and password in the Milo mobile app.