My guess is that the back section of the skirt has a point either side of the centre 'v' and this is what they are referring to. It looks as though it will have a facing. As the other comments say, it's hard to help without sight of the instructions; I don't have this issue of Burda, so I can't look at the pattern and I'm not sure what you're referring to for the 'remaining upper and side edges'. It could be the neckline, but it's not clear.
One thing that helps a lot with the magazine patterns is to take note of the numbers they put at important points; these are indicated on the line drawing in the instructions as well as on the pattern pieces themselves. There are always two of each number and these show which bits to join together.