So if I understand correctly you want to setup an ssid on which users normally have to pay to access it and you want to give them free access for an hour.
If that is indeed what you want to do go to access control of your ssid (wireless > access control). Set the association requirements to open. And the splash page to billing.
Then scroll down and enable the free access for 60 minutes per day.
If you scroll down even further you can define the pricing after the free hour.
Once you save the settings on this page and enable the ssid, the Wireless > Prepaid cards page will become available where you can create extra vouchers for more free access.
More info here:
https://documentation.meraki.com/MR/Splash_Page/Billing_for_Wireless_Access
