Changing the order of your playlists is super easy. Simply open the playlist from My Library > Playlists. Once you are on the playlist page > tap the three dots in the top right hand corner of the screen > click on Edit to make changes. Then long press the 3 bars on the right, and drag each track where you’d like to reorder it. You also will be able to delete the songs here.
Quick Tip: You can look for the pencil icon on the playlist details screen to make the edit quicker.