'Tuning in' a VCR means matching the input radio frequency to that of the signal coming through the aerial. Your system doesn't use radio frequencies at all. The signals are all in 'AV' format (rather than 'RF'). You've correctly set the TV to display an AV input but, from your post, it sounds as if you're trying to get your VCR to recognize a (non-existent) RF signal.
Forget about tuning your VCR. It's completely unnecessary. What you must do is to set it to record the AV 'channel'. There's usually an 'AV' button on a VCR's handset, although it's sometimes labelled 'Ext' or 'Aux'.
Chris