Prepare the tabletop: Strip and sand (if necessary) and clean.
Brush on a gold leaf size - the adhesive coating that the leaf will stick to. Make sure to read the label, especially in regards to timing.
Wait for the appropriate amount of time.
Lay the sheets of leaf carefully onto the size - metal side down - and slide the backing off, beginning at one end of the table and working your way to the other. (They're fragile and small - large sheets would be impossible.) The sheets should overlap slightly; the loose edges will be brushed off so that you end up with a single layer.
Wait about an hour to allow the leaf to adhere fully.
Brush the leaf smooth with a soft brush and remove any excess leaf (blowing is the easiest way to do this).
Wait 24 hours.
Seal the top with polyurethane.