First, you have to add a minimum of $10 to your purchase balance.
Second, you click on the Store and select which credits you want to purchase.
Third, after clicking "BUY NOW", you then select whether you want to add the credits to an existing ad or create a new one.
Fourth, this step is just to confirm the amount of credits you want to buy.
Finally, click "Pay with Purchase Balance", and the exact amount will be deducted from your account.
Each member can only have 1 account. Anybody caught with multiple accounts will be suspended immediately.