When learning logic, it's important to keep the semantics separate from the syntax. This is one of the really big road blocks in getting a grasp on symbolic logic.
Semantics is what the sentence means. "2 is even." That means something different than "4 is even," even if they have similar structures (number is something).
Syntax is just the structure of the sentence. Think of it like the grammar, "Noun verb adjective". A lot of symbolic logic is seeing what can be done with just that grammar. In logic, we are looking at what is called truth-functional connectives. That means they only care about the truth value of statements that they work with, not what they actually mean.
Analogously, even if you don't know the actual words involved, you know that "Adjective Verb Noun" can't be a real sentence in English, because adjectives don't modify verbs.
So, back to your question. The truth value is simply whether a sentence is true or not. This has something to do with semantics, but generally you can look at a sentence and say whether it is true or not.
What trips people up about these questions is they are thinking of "If...then..." semantically. They say, "What does the fact that 2 is even have to do with New York? Nothing. So this is false."
Instead, you should ignore the actual meaning of the sentence and just look at the structure and truth-values. 2 is even, so that part is true. Write a big T over it. New York is a large city, that's true.. Write a big T over that, too. Look at the definition for "If...the...". It should say something like "A->B is true whenever "A and not B" is false." Basically, if A is true, then B better be true, too. Or it will be defined by the truth table. In that case, just look for the right row of the table and see what it tells you.
So, the statement "If 2 is even then New York has a large population" is true, not because there is any special connection between the number 2 and New York, but because of the way "If...then..." works.
Don't worry too much if this seems counter-intuitive. The conditionals we use in logic are probably different than the conditionals that we use in our day to day language. If that kind of thing sounds interesting to you, there is a good amount of research into how natural language conditionals work -> http://plato.stanford.edu/entries/conditionals/