Aurora R4 - How to drain & refill the water cooling unit

Hello everyone,

I've had a quick look online but couldnt find a decent guide to do this, dont want to mess it up either. Can anyone (Hopefully a Dell specialist?) advise on how to drain and refill the fluid in the water cooling unit on the Aurora R4?

My cooling system has started to not be so great, so wanted to try this to fix it, if it doesnt im gonna just buy a Corsair Cooler instead