I installed it by running sudo apt-get install phpymyadmin and then running
sudo apt-get install phpymyadmin
sudo ln -s /usr/share/phpmyadmin/ /usr/share/nginx/html and
sudo ln -s /usr/share/phpmyadmin/ /usr/share/nginx/html
This is the most simple solution. No mapping and all needed.
Download latest phpmyadmin version from here https://www.phpmyadmin.net/downloads
Make a folder named phpmyadmin inside your main root/public folder and unzip phpmyadmin here.
Run yourwebsite.com/phpmyadmin