Hi Russ,
Thanks for your question! Within the custom landing page settings you will see the option to "Redirect to website". Toggling this option to active will provide you the option of putting in a specific URL to direct clients to once logged on. You will also have the option to select the timeout frequency. Please see the below example:
(Please make sure you've downloaded the latest update to the Meraki Go App)
Hope this helps, any other questions please let us know!
Cheers
James