If you’re looking for information about citizenship, you can find it online in the resource center dedicated to this subject. If you’re looking to check your edibility for naturalization, you can do so online by first creating a USCIS account.
Besides eligibility requirements and procedures for applying for citizenship, the resource center also informs you about free study materials and resources for the naturalization test.
If you’re wondering when you should submit the N-400, you can calculate your “earliest accepted filing date” from the USCIS site as well. You’re allowed to file 90 days in advance of your PR requirement if you are a three-year permanent resident who’s married to a U.S. citizen or a 5-year permanent resident.