The dashboard is located within the control panel of your nation.  You are able to access your control panel by logging in through the portal using the link below by replacing slug with your nation's specific slug.

https://slug.nationbuilder.com/admin

After logging in through this portal, you will be routed to your control panel where you are able to take control of your nation's capabilities!  Click here for an overview of how the control panel allows you to manage your nation.