This is how you can pin a window in Oculus:
Go to the virtual desktop at Oculus. If iRacing is running, you can get there by clicking the Oculus button on your controller, and selecting the desktop.
Open the window you would like to pin.
Grab it with the trigger (it works like the left mouse button, you should be able to move the window)
While holding the trigger, press and keep pressed the Grip button.
Now you can release the trigger, and move the window in 3D independently from the virtual desktop. With the thumbstick you can zoom the window or move it closer.
On the bottom left corner there will be a pin visible. Clicking this will pin the window in the oculus.
Now going back to iRacing (clicking the Oculus button) or starting it you will see this window within the game.