How can I allocate more ram to Itunes

I am running a beast of a computer. Everything works perfectly... except Itunes. I have 32GB's of ram. Why does Itunes only use 1. I am watching the walking dead in 1080p and downloading more episodes. I keep getting this pop up that says Itunes is out of memery. I have no idea why that would happen. I have 3TB's avalible I have 28GB of ram not being used and I have a Oct-core processor. Is there a way I can let Itunes use the memory it needs? I can give it 5-6GB and not even have a dent. Please help it is really bugging me. I am on a PC that I built if that has anything to do with it. Thank you.