ahoy!
I can create sections under the content menu but can't create items under the sections I create.
The only item I can see is the default news item under the news section
You have to create some category under the section. In the administrator Menu, under Content you should choose Other Managers -> Category Manager, then add a category under the section that you want. The content items can be create only in the category, not directly under the section.
Regards
Wat