If you are talking about the password to access the community portal, you have to change it directly in your Cisco account.
https://www.cisco.com/c/en/us/about/help/login-account-help.html
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.
