To start with, you must be a lawful permanent resident, which is also known as a green card holder. If you obtained your green card through marriage to a United States citizen, you may become a citizen yourself within three years from the date on your lawful permanent resident card. If you obtained your green card through any other family or business means, it will take five years to become a citizen. Actually, whatever the timing cut off is, you can apply 90 days beforehand. But citizenship will not be granted until the full amount of time has elapsed.
You must also have spent more than 50% of the last five calendar years in the United States.
The naturalization process involves filing form N-400, a biometrics appointment, and an interview and testing. The tests are: American government, and in English test. The English test is exceedingly simple. The American government test is not very difficult, and there are FREE practice exams and sample questions here.
Please feel free to contact me for a telephone or Skype consultation. The cost is USD$105, prepaid by credit card if you are not local to the Sun Valley, Idaho area.