If you see this message:
And can't select an organization or project then you need ask for the owner to add you to the organization.
If you ask the project owner to add you to the project via adding your email address then you should see it appear in the select project drop down.
To be added as an organization member with different permissions the owner/s of the org need to do it through Unity ID, there is a little message at the top of the organization page which the owner will see.
The owner will need to click on Members & Groups then add your email to the organization, then back on the dashboard they can add you as a manager in the Project Members tab.