The right-click menu of many items lets you tag them, for example Managed Resources, Locations, Contacts, Customers, Services and Containers. When you select the Tag menu item, and Coordinates, a new Map popup appears (see Tag) and you can search for an address or click on the map to specify its coordinates. See Map Context for more information about the uses of tagging.
If you want to enter the longitude and latitude of your Open Manage Network Manager installation, this is one way to get it. Go to Control Panel’s Redcell > Application Settings to enter the information.