To tame, you need ghille armor. And you will need fertilized eggs to drop around the nest, i personally have used stego eggs. These eggs will distract the parent and keep in mind that the larger the eggs used, the longer the parent will stay distracted. While the parent is busy, get into the nest, the baby gigantoraptor will run to you and emote. You must press a button with the corresponding emote to tame. Depending on server settings, I find that I can tame a baby and keep the parent distracted using one rock drake egg. And when tamed, the parent will not attack and will stop eating so you can recollect the eggs uneaten.