What kind of radiator is this and can it take TRV
You would remove  the existing vent and add 1/8" pipe up and elbow horizontal. Install the valve as you would a normal cast iron radiator and use a remote mount thermostat device. The heating device you are showing is a convector. You can go to "supplyhouse.com or call 1-888-757-4774" or just "GOOGLE" Dan Foss 1 pipe steam thermostatic radiator valves. Danfoss valve SKU 013G0140, Danfoss thermostat SKU 013G8562 or similar