Congratulations on getting your alpha video working!
You can change the rotation of nodes easily by clicking on the one you want to manipulate in the hierarchy and then going to the ‘Properties’ panel. You’ll want to find the ‘Transform’ section and then change the ‘Rotation’ of your item by 90 degrees on one of the axes depending on the orientation.
For portrait experiences, I usually transform my nodes by 90 on the z axis.
We also have some fun documentation detailing Device Orientation if you want to get a little more advanced. You can find more information about that here.
Hopefully that was helpful!
Have a great day,