Need urgent help - order does not appear

[neon]

Hi

I have just made my first sale today. Payment was done with paypal. As happy as I am, I found that the order was not reflected at the back office.
The only reason I found out about the order is because paypal sent me an email. I desperately need help. What went wrong.

http://farm5.static.flickr.com/4059/4369430313_37bd6afbd7.jpg


Other than that, can someone help me with this:

In order to use your PayPal payment module, you have to configure your PayPal account (sandbox account as well as live account). Log in to PayPal and follow these instructions.

In Profile >> Selling Preferences >> Instant Payment Notification Preferences, set:

•Instant Payment Notification (IPN) to On
•Instant Payment Notification (IPN) URL to http://localhost:8888/prestashop/modules/paypal/validation.php



What is http://localhost:8888/prestashop/modules/paypal/validation.php ? I copy the address to paypal, but it does not work. what is localhost:8888?

Please please help me. I have been on this thing for hours.
Thanks