To add an item to the Content Center:
1. Navigate to Content Center
2. Click the Add Content Button and choose which type of content to upload (URL/File/Box file)
3. After adding the content you can edit the item's metadata information (items’ title, description and image) and decide whether this item is visible in the Content Center or whether it is private so only you can access it from the private list.
4. click Add. The item will now be visible and you can add it to your boards.