Spotinst allows you to manage your users in a very easy and flexible way across your Organization and accounts.
In order to add users to the organization, open the Settings in your Organization:
Under the organization tab, you can manage Admins (Users that holds editor permissions to all the accounts in the organization) and Users (Editors/Viewers).
Here is how to add new or existing users to accounts:
Choose if it's an existing or new user, the user's email, role (viewer/editor) and to which account you want to add the user (dropdown with the existing accounts):
At the Account level - you can see the list of users in the current account and add existing users from the organization, or create new users.