Nissan Pulsar Q 1990 hatchback - we cant find the petrol cap release???

Hi we can not locate the petrol cap release on our car...we've looked in all the usual places down beside the seat under the dash even on the dash..... but no obvious button or lever. The car has only recently been purchased for our so who is learning to drive and it's almost out of petrol. Can anyone help us please. Many thanks Therese