Hi @nicollesophie you can change member access in the admin console. If you are not the current Admin of the plan, then you will need the Admin to do that for you.

More details here - https://help.miro.com/hc/en-us/articles/360021990719-Manage-Free-Plan

Hey Paul, 

I am the Admin and I don’t have this option. The only option I have is to “Revoke Invitation”, when I click on the three dot next to the member.

That means the person doesn't have an active account yet. They will need to accept the invitation first, then you can make adjustments to their account.