Adding ports

From the looks of it there's not much support in this app because nobody's questions are answered but How in the WORLD do you add the internal part of your port to your box?? This is the most frustrating app I've ever used and is super glitchy.. I have my basic box dimensions but trying to add an L port. All it does is cut a hole out but there's no actual port.. definitely not paying however much I'm paying for the pro account. Won't even let me add favorite speakers, keep trying to get me to go to pro which I already have.. definitely cancelling this subscription