Bang them in a sink/bath full of hot water for abit, then empty and wear! A long as you can live through having wet feet for abit you'll find that they'll be broken in after about a day!
Hope this helps.
Put boots on with the insoles in and sock on you'll wear with them. Stand in bath full of hot water moving about, bending toes etc. Water will seep into boots slowly. Keep doing this for about an hour. Get out, boots off, stuff with newspaper, let dry slowly (days not hours, not in an airing cupboard or on radiator). Polish. Take paper out. Wear loads.