Hi Leonard,My name is ***** ***** I will assist with your query today.
The box you have requires a terrestrial aerial, you can put internal aerials such as the one found here for under £20.
Should you wish to have an external aerial, you would need to install this on your roof\loft, and the run a coax cable to the TV receiver, then terminate the cable with a push fit coax plug. You can find a suitable external terrestrial aerial here.
Please let me know if you need anything clarified.
Leanard, just wondered if you need any further assistance, and would appreciate if you could rate the service received to date.