How can I tune my Sony Trinitron digital Tv to Freeview please?

My daughter and her husband gave me their Trinitron TV when they bought a flatscreen TV. The set works fine when tuned to Virgin Media cable box and I get four main terrestrial channels on analouge.[green printing in top right corner.] My son-in-law maintains they had the integrated freeview tuned in digitally but all I get is message saying no stations saved. He has tried without success to tune it as they had it without success. I have an almost new UHF aerial whereas my son-in laws aerial is at least 10 plus years old. Can you help please as I would like to loose Virgin and go over to Freeview hopefully without getting another seperate Freeview box. Thanks in anticipation