In order to get more coins than what you get as free airdrop:
1) login to coinpayments account
2) open wallets tab
3) select Coinpayments coin and click convert button. Here you wil get all coin conversion options to get discounted cps coins until end of June
He wrote #3 a little backwards, you click the Convert To next to the coin you are purchasing with then pick CPS Coin in the dropdown. For example if you are using BTC click Convert To next to BTC, then CPS Coin.