When you start DCP-o-matic for the first time it will ask you if you want to use ‘simple’ or ‘full’ mode.
The difference between these two is that some of DCP-o-matic's more complex or less-used controls are hidden from view in ‘Simple’ mode. This makes the interface simpler to navigate. You may wish to choose this mode if you do not have much experience with DCP or video processing.
Even if you choose ‘Simple’ mode you can always go back to ‘Full’ mode by changing the Interface complexity setting in the General tab of Preferences.
All the screenshots in this manual are from a copy of DCP-o-matic in ‘Full’ mode.