This topic will help you with question part 1 Information about your eligibility for the united states citizenship application form n400 of USCIS

On question B of Part 1 of your name for the N-400 form Application for Naturalization it asks:

Your name exactly as it appears on your permanent resident card

This question is pretty straight forward. All you have to do is look at your green card (front side) and see how the name appears on your green card.

For example, look at the example Front side green card (or permanent residence card) I have posted here. Base on the example green card, you would fill out the form as:

Family Name (Last Name) = Tulip
Given Name (First Name) = Yellow
Full Middle Name (If Applicable) = Flower

NOTE: the comma in the given name, separates the first name with the middle name. In some cultures, the names can be complicated, however, you have to change the format to fit the United States format. lets say for example, My father who is from Spain has a very long name, as is traditional in Spain to have long names, so lets say for example, my dad's full name is: Francisco Alejandro Chavez Rodriguez, in this case, this would be formats:

NOTE: also note that the names are different on the front and on the back of the green card, on the back, you dont see 'Flower', so always use the name as it appears on the front side of the green card if the front and back do not match. however, in most cases, it will match exactly.

Spanish Format:
Patenal Name = Chavez
Maternal Name = Rodriguez
First Name = Francisco
Middle Name = Alejandro

U.S. Format
Last Name = Chavez Rodriguez
First Name (First Name) = Francisco
Middle Name (If Applicable) = Alejandro

I realize this is not as straight forward as it may seem on some other parts of the world. The USCIS (immigration services) realizes the complexity of different cultures around the world. My best advise to you is to think like a lawyer. Don't make it complecated. Think about what the questions is asking. in this case, is asking you to look at your green card and provide the information EXACTLY as it shows on the green card. Don't add or remove any characters.