As mentioned above, you are most likely going to have to price this as a "multi-city" itinerary. If you have a preference in airlines, most will have that option on their web-site. If you don't care, then a site like Kayak.com or Google Flights will also offer that option. When entering each leg, just be sure to set the dates to allow the time you want for that layover.

I agree that the ITA matrix might be a bit much for a first-timer. I use it a lot but it is not very user friendly. It also seems a lot slower and more prone to database hang-ups since being acquired by Google.