Adding a node makes an icon for it appear in the main window's nodes area, which allows you to display the node's metrics and run scripts on it.
To add a node:
Click in the Group field and type the name of the group (new or existing) the node is to be added to, or choose the group from the drop-down list.
Click in the Node field and type the name of the node to be added.
Click on Apply or OK.