To install phpmyadmin just execute this command:

sudo apt-get install phpmyadmin

Then you need to go to

http://localhost/phpmyadmin

PhpMyAdmin should now work. But if the above url gives you an error:

Not Found
The requested URL /phpmyadmin was not found on this server.

you need to check two things.
1. Open file:

/etc/phpmyadmin/apache.conf

and look for alias /phpmyadmin. It should look like this

Alias /phpmyadmin /usr/share/phpmyadmin

2. Check directory:

/etc/apache2/conf.d

There should be a file phpmyadmin.conf which is a symlink to

/etc/phpmyadmin/apache.conf

If it’s not there, create it with this command:

sudo ln -s /etc/phpmyadmin/apache.conf /etc/apache2/conf.d/phpmyadmin.conf

After this, you just need to restart the server and enjoy your phpmyadmin installation.