The manual says the system takes (from dry), one liter of "extended life" 50/50 coolant. I don't know what type is used but there are brands out there that will mix with any type of coolant, extended life, standard, etc. If in doubt or unsure of the quality of the coolant in the system, just drain it out and refill it with a liter of the best stuff you can find. The manual also says to replace the coolant every 18,000 miles (28,900 KM). If you buy the "straight" stuff, make sure you mix it 50/50 with distilled water.
If you decide to drain and change, you need to take off the cowlings to access the radiator cap and remove it. Then take off the inlet hose to the water pump which is located just behind the motor controller on the right side of the bike. Drain the coolant---you could also flush it with water at this time if you wanted to. Reconnect the hose and then remove the vent plug. If you have the Parker motor, the vent plug is located on the left side of the motor near the forward top edge of the plastic end cover that protects the motor wires. Remove the plug with an Allen wrench, add coolant until the coolant starts to come out of the hole and replace the plug. Add the rest of the coolant, replace the cap and you are done. Ride check the bike for leaks and make sure the radiator is warm to confirm that there is no air lock in the system. BTW--if you have the IEC motor the vent is a plug in the motor housing near the top on the left side. It is removed with an Allen wrench and has a copper crush washer under it. Same vent procedure as the Parker motor.