I had been looking at how to do this and usually just find old .deb files but, I don't like using 5 year old .deb files that are for another version of Ubuntu.
So here is an easier way:
sudo apt update

sudo apt install git libtool pkg-config libwnck-dev libwnck-3-dev debhelper gtk3-engines-xfce libcairo2-dev libdecoration0-dev libxrender-dev libx11-dev gettext intltool intltool-debian libltdl-dev libtool autopoint automake build-essential libxi-dev

*g++-aarch64-linux-gnu --- this package may not be required to compile I leave it at your discretion whether to install it or not. 
(I left this out of the above command because I had to remove it afterwards but, it's up to you to install it if you want.)

(You may want to create a directory for these if you want, It will create 2 directories one emerald and the other emerald-themes. I created a folder in my Downloads directory called emerald that had both directories in it.)

git clone https://github.com/compiz-reloaded/emerald

git clone https://github.com/compiz-reloaded/emerald-themes

Change directories were the emerald source is, then do the following commands, the same applies for the emerald-themes directory:


*Optional step - Configure after autogen.sh is done configure with:
./configure --prefix=/usr


sudo make install
Here is the YouTube video I got this from: I mainly just went by the commands but, feel free to listen to the video as there is some explaining of what is going on in the video.


Then go into CCSM Window decoration and put this in the command: