Difficult to say, because you didn't describe what steps did not work.
In the Playlist view you can use the same procedure to remove any files from the Playlist. You cannot make a quick Playlist from an external drive or network source.
My guess is that you can't see your made playlist here?
The playlist menu is someway hidden
Goto the Media Library menu, and in that menu scroll up or down with the keys on your remote. You wil find the Playlist menu.
If you added music files with the remote control, you have to goto the Music tab on top of the screen by pressing the <right> key on your remote. Same for Pictures and Movies, go to the right tab to see your playlist content.
When under the <All> tab you will not see anything.