Nurse identifies Romeo for Juliet in Act I, scene v, lines 142-143, "His name is Romeo, and a Montague;/ The only son of your great enemy."

If you have a textbook or copy of the play, you can skim the scene you are trying to find the quote in until you find it (old-fashioned, I know), or, like the previous response, use the "Find" function to search for key words in the quote from the etext version of the play.

The Nurse identifies Romeo at that point.

To find specific character quotations, I'd suggest opening the etext of the play and using the "Find" function. Then you can look for specific words or character names.