This is my PSA in case anyone else runs into the same issue we just had with the common app! While it is very common sense, it took us a minute to figure it out, and I want to save someone from having a heart attack at 11:59PM on their application deadline date!
When we clicked “submit”, it pulled up a PDF to preview. Even though we scrolled to the bottom of the page, we could not get it to reveal a “submit” button (it’s actually a “continue” button. The solution was to click the “full screen” button in the upper right of our computer (the double arrows that appear on a Mac when you hover the mouse over the upper right corner of your screen). Once we had full screen, the “continue” button was revealed at the bottom.
It, of course, was my daughter that figured this out. I’m sure all of the teenagers are rolling their eyes at me (and maybe some parents too), but I’m betting any parents that are reading this are thanking Jesus that I posted this! Hope someone finds it helpful! 
The way to avoid the panic, of course, is to not wait until the deadline to apply, but what fun is that?!