You've not said what equipment you're using. I'll assume that you've got a Freeview box but the basic principles will probably also apply to 'integrated' TV's and Sky boxes:
The ITV2 signal which leaves your Freeview box is in the form of separate audio and video signals (and not as a radio frequency). For this reason, you can't tune your video recorder to receive the right radio frequency (because there isn't one). What you need to do is to tell your video recorder to record the audio and video signals directly. To do this, you need to set the channel to be recorded to 'AV'. The video recorder will then record the output of the Freeview box (assuming, of course, that they're connected together by either a Scart lead or by AV leads). So, as long as the Freeview box is set to Channel 6 (ITV2) you'll be able to record your chosen programmes.
Chris