#4 Create the directory which will be used to host the file and give wikileaks user's write permissions:
mkdir /var/www/wikileaks.mydomain.com
chown wikileaks:wikileaks /var/www/wikileaks.mydomain.com
chmod u+w /var/www/wikileaks.mydomain.com
#5 Create Apache virtual host
nano /etc/apache2/sites-available/wikileaks.mydomain.com
# With the following content (modify it according to your needs)
<VirtualHost *:80>
ServerName wikileaks.mydomain.com
DocumentRoot /var/www/wikileaks.mydomain.com
<Directory /var/www/wikileaks.mydomain.com>
AllowOverride None
</Directory>
<Location />
Order Allow,Deny
Allow from All
</Location>
</VirtualHost>
#6 Enable the vhost
a2ensite wikileaks.mydomain.com