To arrange your media in a specific order, within Media Manager, select Manage Content on the side menu
Click on the Category (or further into the Sub Categories) in which the files you wish to arrange reside.
From the list of files, select the file you wish to move by clicking on the double arrow to the left of the file name. Drag the file to the desired location in the list.
The files will display to the end user in the same order as shown in Media Manager.