Practical order.
WHAT TO DO IN ORDER
Connect and configure the router Change its administrative password Apply firmware updates Configure the wireless network Configure a guest network Connect the switch and wired devices Connect wireless devices Test everything
WHY THE PASSWORD FIRST
Default credentials are published.
WHAT TO CONFIGURE ON THE ROUTER
The address range for the network Address reservations for fixed devices The firewall, left enabled Only the features you use
WHAT TO RECORD AS YOU GO
Addresses assigned The wireless password Administrative credentials, in your password manager
WHAT TO TEST
Internet access from wired and wireless
Access to local resources: printers, shared storage
Guest network isolation
THE ISOLATION TEST
Connect to the guest network and attempt to reach a business device.
You should not be able to.
WHAT TO DO LAST
Document it.