First decide what will be the forward mA into the opto isolater LED ( typically 10 to 60 mA )and then get the forward voltage drop ( about 1.15V)of the LED in 4N35 from data sheet. Subtract this voltage from the 110 +30% value to get the voltage that has to be dropped by the resistor. Now you know the Current and Volts and finding the requisite resistance is homework.

Just cross check on the power dissipation of the resistor as you are going to drop a "big" value across the resistor. And for this reason keep the LED current at about 10mA or so...I am not sure about the circuit on the isolated side and hence cannot decide this value.

Raghu