Well, get as much time in on your mtb as you can until the road bike is ready. I assume you're having the Orbea professionally fitted to you? Be sure to bring your mtb to the fitter to compare / transfer key dimensions and so you can talk with the fitter about what works and what doesn't.
Generally, you want to get miles on the bike. Most working people try to fit in long rides on the weekends, and at least 2-4 rides during the week. You may wish to purchase a trainer for indoor work, or lights and reflective gear for night riding. In addition or when you can't ride, basic calisthenics, "core work" and general yoga / flexibility work is helpful.
You'll also need to learn "roadcraft" or how to ride a bike effectively on roads and with traffic. Local cycle clubs are a good way to do this - hit google, type the name of your town and "bicycle club" and get in touch.