Well, we already have avian dinosaurs everywhere. Just start breeding them with an eye toward creating non-avian dinosaurs eventually.

Like the ones in Antarctica?

Yeah, start with non-flight dinosaurs like penguins, ostriches, and chickens.

We’ll never see them alive, air is too thin now.

VR is the next best way.

Dinos need fat air? Because they were so big or?

The theory is they needed more oxygen-rich air because the square-cube law means an animal 2X the length, width, height of an elephant has 8X as much mass to deliver oxygen to. The heart can only work so hard, and as far as I know, there has never been a land animal with more than one heart or one set of lungs.

I'm not sure if this theory is still accepted though, as it seems the current consensus is that the air was actually less oxygenated during the dinosaurs' lives.