Procedure to apply for FBI Clearance/Police Certificate from US

My brother in law has recently become eligible for Canadian Citizenship. He already cleared his citizenship test but CIC has asked him to produce a police certificate from the USA since he has spend a few months in the last 5 years while visiting us in the USA. What would be the easiest and fastest way to apply for his FBI clearance since CIC has officially given him 30 days to come up with the said document or else inform them about the progress. Also, what time frame of the past years does FBI police certificate cover by default?
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