It is for existing atrader users. If you register on the site, download the program, youll have an email and token which you can use to register on the site for the airdrop.
http://www.atrader.org/register.php

Download the wallet to get the wallet address and sync to the blockchain.
You then get emailed a token which you can use to register for the airdrop here.
http://www.atrader.org/registerwallet.php
Obviosuly you dont need to use the trading software as it stands at the moment, but as the project progresses, you should be able to use ATC later to trade

Regards atradercoindev.