There are two little lighter coloured buttons on the outside of the carrycot, where the hood hinges. These are near the buttons that allow the carrycot to clip and unclip from the buggy frame. They are flat on top and sort of rounded at the bottom.

Press them down (on mine they seem a bit loose, and wobble slightly as you press them). You have to press them quite hard, but should then be able to push the hood down.

I find I have to nudge the hood with my head to get it started, it can be a bit fiddly.

Hope this helps.