To use the layers theme engine please follow this guide in the YouTube video, but remember you already have the layers app built in to this rom, so you don't need to worry about joining the community or downloading the beta. See the XDA page below for available themes (you can also go to the Google play store and search "layers themes" - if you install themes from the play store make sure you open the theme after downloading and follow instructions from there)Here is the youtube guide https://youtu.be/jfsVp57CSnY