That module has the switching transistor and kickback diode onboard, good to go, just remember those relay coils draw about 75 mA, so size your 5V power supply accordingly.
R1 is a 150 (15 + 1"0") Ohm base resistor for the NPN transistor (Q1) and LED current limit.
3.5 mA from GPIO pin should be fine, datasheet says 12 ma max, if relay pulls up with a HIGH thats OK, some are switchable, most "opto isolated" boards use low true logic.