From 35 W:
take the 35th-36th Street exit.
Go east on 36th street (it's a one way).
When you get to Park Avenue, turn left.
Go on this for a while.
Then make a left on 26th Street.
You'll cross back over 35W, and Stevens Avenue is four blocks ahead.
Turn left onto Stevens Avenue.

You can park on the left side of the street, or on neighboring streets.
The glass door has the numbers 2609 painted on it, and above the door is a metal sign that says "Fallout".