How to manage the received contents?

To access the content sent by your users, go to My app > Content > Sections. Hover over your Submit section and click on the View content button.

You’ll land in the content management page

Here you can manage the publication of this content. Either in bulk by using the checkboxes on the right of each content line. Or on a case by case basis by clicking on the content you are interested in. 
This way, you can in one click modify and publish the content received from your users.