Bar codes first then check list and the the rest of the application/ documents. Just as Jeleni said, it is specified in the guide. There isn't a need to ask the same question so many times!
Putting the application together can be quite stressful, and u can make yourself sick with all the itty bitty details, so it is best to educate yourself (like you are on this forum and through the application guides) and then sort of just let it all go, and submit the application. One of the scariest moments for me was actually handing it over to the courier and trusting that it was all done properly, but if u don't let it go, then the application will never be submitted!