Station identification is required by the FCC once per hour, as close to the top of the hour as programmatically possible. Station identification consists of station call-letters and community of license. Hence, for WMUA legal station identification is "WMUA, Amherst."
If you find that you've missed identifying the station at the top of the hour, IDENTIFY IT AS SOON AS POSSIBLE. Do not just let it go, and wait for the next hour. This is VERY important.