This is the link:

https://www.digitalocean.com/community/articles/how-to-install-and-secure-phpmyadmin-on-ubuntu-12-04

This is how to create the htpasswd:

sudo htpasswd -c /path/to/passwords/.htpasswd username

and this is how to change it later on:

sudo htpasswd /path/to/passwords/.htpasswd username

Ref: http://wiki.ultraseedbox.com/index.php?title=How_to_change_passwords