issues installing smart radiators- iflo valves

Hi, I’m trying to install the smart radiator valves. However, I’m having difficulty. I can screw the smaller section on the radiator, but unable to then fit the ‘smart section’s I think this is because there isn’t enough depth. I think I need an adaptor but unsure which one and how to fit it. Help much appreciated 🙏

Updated- I have a photo but not sure how to attach it. The current radiator head says iflo