I believe you are talking about TACACS authentication, which does not apply to the Meraki dashboard.
Correct me if I am wrong. In any case, here is a guide on how to configure authentication via CLI.
Configure Change of Authorization in Catalyst 1300 Using Web User Interface - Cisco
Cisco Catalyst 1300 Switches Series CLI Guide - AAA Commands [Cisco Catalyst 1300 Series Switches] -...
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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