1. Go to the main page of your course.
2. Click on Edit mode on the top right of the page.
3. Click on the 3dot dropdown menu on the right-hand side of the course items. Click on the four-headed arrow Move icon (note that clicking and holding will initiate the drag-and-drop process). 
   
   
   
   
4. A dialog menu will pop up listing areas in the course where you can move the item. Click on the item location where you wish to move the course item.
   
   
   
   
5. The course item will now be moved beneath the selected location.
   
   

Move a whole topic:

To move the contents of more than one item at a time, you will have to move the entire Topic section using the same method: 

1. Go to the main page of your course.
2. Click on Edit mode on the top right of the page.
3. A Move icon will appear under the 3dot dropdown on the right-hand side of the Topic name. Click on the four-headed arrow Move icon. 
   
   
   
   
4. A menu will pop up. Click on the location underneath which you wish to move the course item.
   
   
   
   
   

Note: If the Topics have kept their default numbered names, they will be renamed according to the descending order (e.g. Topic 1, Topic 2... etc.). If you move Topic 2 above Topic 1, Topic 2 will become Topic 1 and Topic 2 will become Topic 1. But if each topic section has a custom name, then the custom name will remain. Please take a look at this article to customize topic names.