Unfortunately if you haven’t ridden on busy roads before you should return the trike if you can.
The first thing to do is rent a tricycle and take it on the road. If you have a fear of riding in cars, I can’t imagine how you will feel when cars and trucks are zipping by you at 40+ mph with no regard for your well being.
And others have pointed out valid safety concerns. Just go to a park and watch kids on trikes cornering at high speeds.
I don’t want to discourage you from biking, but you need to understand the environment and issues with a trike.
John