Credit card, paypal, money order, check are the accepted forms of payment. You can buy some thing off the site of equal value, but make sure you let Yangdu know that you are doing it so she doesn't send you the item from the site rather then the DOTD that you wanted. Be sure to include your payment option, full name and address, as well as what item you like (be specific since there are many DOTDs and normally multiple items).
Happy sharking.