In the home screen of the Zmodo app, press the gear icon in the top right of your device's listing to access device settings. Choose "General" settings then press “Device Name” and type in the new name for your device. Then press "Save" to save your changes.
You can also rename your device through the web app at user.zmodo.com. Within the My Devices page, mouse over the device and click on the gear icon to access the device settings. Then follow the same steps as the mobile app (General > Device Name) to change the name of your device.