I installed it by running sudo apt-get install phpymyadmin
and then running
sudo ln -s /usr/share/phpmyadmin/ /usr/share/nginx/html
and
For another alternative that I found super simple and that worked right out of the box I set up a new Nginx site from inside the Homestead box using the serve.sh script:
serve adminer.app /home/vagrant/Code/adminer/
And then in there I dropped the one page successor to phpmyadmin, Adminer. I also renamed it to "index.php" to make it just work. Then after adding the adminer.app entry to my hosts file I was good to go.
Had not used a web based MySQL interface in years since I just didn't like maintaining phpMyAdmin but this one is sweet. One file (plus an optional CSS file if you want a nicer theme) and that is all. Easy to maintain and update.