The easy way is to bias the current transformer at half of the ADC's reference voltage. Using a second ADC input to monitor the bias voltage will reduce DC bias error.
If you have a 10 bit ADC (1024 steps) with a 5 volt reference, then each ADC step is 5 / 1024 = 4.883 mV. That is just under half and amp for a 10 mV/amp CT. The span would be about 2.5 V / 10 mV = 250 amps.
float amps = (ADC1 - ADC2) * 500.0 / 1024.0;