Is mysqld running?
Check: from terminal as a user who can sudo or is root user:
ps aux |grep mysqld
ps is a command to show running processes ... aux are switches to the command
the | symbol is a pipe to run the output of ps aux through 'grep' showing only processes that pertain to the MySQL Server (mysqld).
Future note: things that end in 'd' could be daemons ... ie server apps.
You might see some line that looks similar to this (from CentOS server):
mysql 6951 0.2 1.7 627380 281048 ? Sl Oct09 162:36 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/log/mysqld.log --open-files-limit=5000 --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/lib/mysql/mysql.sock
That means it's running and if one studies that line it provides a wealth of information … log error, process ID file, etc.
For PHPMyAdmin ...
The button that says 'Install' points to: apt://phpmyadmin
But would imagine one could also download the .gz for PHPMyAdmin
Un-gunzip it, shorten the resulting folder name to something like 'phpmadmin' (mv "longtime" 'shortname'), move the resulting shortname folder into web root, change ownership/permissions on the folder and it's contents, then access with a web browser.
There are docs for PHPMyAdmin @:
'spirit of sharing', Ken