You'll find . . . . . . . . information you need at . . . . . . . . top of . . . . . . . . page 15.

The definite article 'the' is used before specific things. Here, we are referring to the specific information that 'you' need. Hence, we must use 'the' before it. No article is used before proper nouns. Here 'page 15' is a proper noun. Therefore, no article is used before it.