Linux / Ubuntu:
If installed phpmyadmin via apt:
sudo apt-get install phpmyadmin php-mbstring
Can check /etc/phpmyadmin/config-db.php
for changing the user credentials.
$dbuser='pma';
$dbpass='my_pass';
$basepath='';
$dbname='phpmyadmin';
$dbserver='localhost';
$dbport='3306';
$dbtype='mysql';