You can view your own playlists by clicking the Playlists button on the sidebar.
All of your playlists, published and unpublished, will appear in this menu.
To view another channel's playlists, you'll first navigate to their channel page. From here, select the Playlists tab.
All public playlists created by this channel will appear here. Any playlists that haven't been made public will not appear here and aren't viewable for anyone except the channel who created them