You can either get dual filament sockets with 1157 bulbs, and wire the dim filament to the parking lights (corner light) and the bright filament to the turn signal.

Or, with the bulbs and sockets already there, wire one side of the bulb to the turn signal positive, and the other to the parking light positive... then they will blink as a turn signal all the time, as well as be on with the parking lights. When the parking lights are on they will still flash as well.