Playlists

You may create any number of playlists containing the files you have on your iPhone/iPad.

To create a new playlist tap the "Edit" button, then tap the "New" button, name the playlist and tap "Done".
To rename a playlist, tap the name when in edit mode.

Now select the newly created playlist by tapping on it which will take you to another view where you add the songs.

Tap the "Add Songs" button at the bottom tool bar and select the files you want to add from the displayed song picker.
You may also edit a playlist with the ordinary iOS commands for deleting and moving files.

Tap a file to start playback.

If you enable "iCloud Playlist Sync" in the "Settings" view, playlists will be synchronized between all your iOS devices. However, Amazing Slow Downer is using the simplest way to do this meaning that no data will be stored in iCloud, instead all data is "pushed" between the devices. This means that the device that does the last edit will "win". To avoid any problem with playlists not being synchronized correctly, only make edits on one device at the time or at least wait until all edits have been "pushed" to the other device(s).