The New Goblin, Venom and 5,000 Upgrade points are unlocked when you enter these codes using the D-Pad when you are standing in the helicarrier. If you have entered the code correctly you will hear a tone as confirmation and they will be available for selection at the 'Sidekick Select' console.
Unlock New Green Goblin: Left, Down, Right, Right, Down, Left.
Unlock Venom: Left, Left, Right, Up, Down, Down.
Get 5,000 Upgrade Points: Up, Up, Down, Down, Left, Right.