often on VAG cars there is a drain tap at the bottom of the radiator on the pipework joint.
No tools required, if there is one you will see an outlet, its a case of pulling/twisting the tap to drain. (with coolant expansion tank lid off).
Once emptied remember to do the tap back up!
Then to refill simply fill via the coolant expansion tank, best to 'Pre-mix' the coolant to get the right mixture. as for qty, expect around 4 - 4.5 ltires if FULLY drained, but some see only 3 litres as sometimes its not so easy to fully drain depending if you clear out the heater matrix etc.
then when it stops taking in any more coolant, leave top off and start car, monitor the level it will likely drop and keep filling to maintain the level. they tend to be self purging systems so leaving it running will purge the air out, you will need to leave it ticking over till its at operating temperature so the thermostat is fully open and you get good circulation.
Once done, turn car off and allow to cool. BUT leave expansion tank lid on but not done up. this will allow the pressures to settle as the car cools, the level will likely drop a bit when you return to it after cooling, top up. then do lid up. Then keep monitoring over next few days in case any last bits of air work there way out.
*edit* when refilling and circulating, have the heaters on. not 100% sure this is required but this at least confirms the whole system is open and circulating.