@nst1 Are both access points broadcasting the same SSID's or are they broadcasting different networks?
Either way Wireless > Radio is where you need to go the change your settings.
If you go to "Wireless > Configure > Radio settings > RF Profiles" you can either edit or create a profile and either set the radio power, or set it to auto and let it automatically adjust based on neighboring APs.
If you only have two MR42's you don't have an issue. They are highly probably to choose two non-overlapping channel sets, and will not impede each other.