A device in CIS can be activated/added by clicking Devices > Add and filling in the requried information and then click Save Changes. To create a new device you need the following:
device name
provider device id (Sigfox Module ID, LoRa DEUI etc.)
description for your device
select the approriate message decoder from the drop down list
select the application to which you wish to associate your device
leave the Automatically Update Coordinates switch turned ON if you device is equipped with a GPS add-on board
Recommendation - use the device serial number in the device name. This is helpful if you have many devices as you can quickly find your device just by typing the serial number in the Name filter on the top of your device list.
The last step before you turn ON your devices and start receiving messages is to past the callback URL (see Create Application) in your connectivity provider portal.