Basically the operating frequency is: Base Frequency + (channel # * channel spacing). The channel spacing is found in the MDMCFG0 and MDMCFG1 registers. Channel number is in the CHANNR register. The initial values being used are being set in the Components\mrfi\smartrf\CC2500\smartrf_CC2500.h file
You can load register values into SmartRF Studio in a CC2500 device in off line mode to also see this information.