Account Settings > Groups
The default Group is Administrators. Members of the Administrators group have View and Edit access to every dashboard in the account.
Additional Groups can be added and managed independently. A Group can have multiple users, and define access to dashboards.
To begin choose Edit Group from the ellipsis menu on the Group row.
Manage Group Details
Check or uncheck users to add or remove them from the Group.
Dashboard permissions
Checking or unchecking the dashboard permissions affects how members of this group can interact with dashboards (one more reason why it's good to name your dashboards something explicit and clear).
View: This is a 'view only' setting, so if you have users who need access to see the selected dashboard, and not edit the contents, this is the setting for them.
Edit: This allows full access and editing capabilities to the selected dashboard, for everyone in the current group.
All changes will be saved automatically.