You can see and remove the servers you wish to monitor under the Administration tab > Servers of Server Genius:
Add a new server by clicking on the "Add a new server" button, you will then see this interface:
Follow the procedure by downloading Server Genius Agent on the new server you wish to add:
As for Server Genius setup, agree to the License, then select the destination location folder (by default, it will be installed on C:\Program Files (x86)\RDS-Tools\ServerGenius Agent):
Then, enter the main server URL:
Click on install:
Then click on finish to exit the Setup.
Run the agent and your new server should be visible on the Servers Management interface and on the Dashboard: