How to get to the foundry? Once you have beatin scorpion at netherealm, you can now go to the foundry. The foundry is at the tornament place with the tokens. It will be open to face shang tsung.
If you want to know how to get sub and scorpion another way then you might as well use cheat codes:
play as Scorpion
At the main menu, hold L2 then press Square, Up, L1, R1, Left, Right, Square to unlock Scorpion in Versus mode. If you entered the code correctly, you will hear a sound. Alternately, successfully complete the game with Liu Kang to unlock Scorpion in Single Player and Co-Op mode. To unlock Scorpion in Versus mode, in the Foundry area, follow the pathway downstairs to the left of the save point. Two archers will break through the wall. Throw one at the wall to the left of the doorway to break it open, giving you access to a hidden room full of lava and a Ying Yang on a ledge. Grab one of the archers and throw him into the lava. Then, double jump off his back to get the Ying Yang that unlocks Scorpion in Versus mode.
Play as Sub-Zero
At the main menu, hold L2 then press Square, Down, Up, L1(2), Up, Square to unlock Sub-Zero in Versus mode. If you entered the code correctly, you will hear a sound. Alternately, successfully complete the game with Kung Lao to unlock Sub-Zero in Single Player and Co-Op mode. To unlock Sub-Zero in Versus mode, take the boat ride across blood lake. You can find Sub-Zero's Versus mode icon in back of the lion-like statue to your left (when facing the big door). Run along the wall and double jump at the end to collect it.
mortal Kombat 2 arcade game
At the main menu, hold L2 and press Square, Up, Down, Right, Left, R2, Square to unlock the classic Mortal Kombat 2 arcade game in the Kontent menu. If you entered the code correctly, you will hear a sound. Alternately, successfully complete all five Smoke missions. Note: This feature is not available in the European version of the game
If the code don't seem to work then keep trying till you hear a sound. Just don't give up.