Pretty easy to sit the newborn up - hold the receptacle between your legs and sit them either side on, or bub's back to your belly. You don't have to start straight away, either. DD was 2 weeks old when I bit the bullet and has been fully continent for over 18 months, she's now just over 2.5yo
See if you can find a vintage enamel chamber pot, or even a ceramic/china one if you have soft floors. They are much easier to handle than potties for a newborn, and I never had a spill with ours.
Your newborn will amaze you! If you felt clever with your DD at an older age starting EC, a newborn will humble you and you will feel that the new baby is far cleverer than you are