If you are running Linux and have shell access, here is one way:
First create a file called .htaccess in the folder you want to protect (ex /web/seattleone/admin/ ).
It's contents should look simular to this:
AuthUserFile /web/seattleone/admin/.htpasswd
AuthGroupFile /dev/null
AuthName Admin
AuthType Basic
require valid-user
In your shell, cd to the protected folder and enter the following (replace neux with your desired username):
htpasswd -c .htpasswd neux
It will then prompt you for a password.
That should work.