In the old Itinerary Builder interface the blue navigation bar used to be displayed vertically along the left hand side like this:

Now main navigation bar  displays horizontally and at the top of the Itinerary builder. When you open a trip to edit here's what this looks like:

This change to the interface was done to make it easier to access quick tasks like Previewing an itinerary or removing a traveler from a trip. 

In the top navigation bar you can edit your Trip Settings, add multiple travelers for group trips, Preview the itinerary and send it off to your clients. Check out these articles below that explain the different pieces of the new navigation bar.