To add a new device to be monitored by OverTime, select the device on the OpenView map. Let us say we want to monitor TestSwitch1900 in the below map:
A window like the one shown here will appear showing the progress of the addition:
At present the map is showing "Router-1" as being selected. You would need to click on "TestSwitch1900" first. Then, open the Misc menu item and then select OverTime Actions, then select Add/Update Target/s.