First navigate to the playlist overview page.
If you are positioned on the “All my Songs” page just use the back button of the app or in the left side menu.
Then select the plus button in the side menu (1) and select “New Playlist” (2).
In the following dialog enter a name for the playlist (1) and close the dialog with the Save button (2).
After the playlist is created SongRepertoire automatically opens the empty playlist page. Because it is empty you see some information about managing playlist content.
Details: Add songs to playlists.