For MAC Based Authentication you need to have an In-house Radius Server.
Meraki does not offer a Radius Server with MAC Based Authentication.
Once you have your own independent Radius Server either on Windows or Linux. You may connect the same to Meraki SSID.
Your page may look like below with the IP address and secret key configured on your Radius.
Incase you want to use Meraki Radius server which will do only Username based Authentication.
You need to create User Account and Authorize them with the time the access is allowed for. You can create Users under
Network-wide -> Users
However prior to this you need to associate your SSID with Meraki Radius. You can do this under
Wireless -> Access control
Your page may look like below
If required you may also customize Splash page (Landing / Welcome / Captive page)
Wireless-> Splash page