There is a box where you can put a price, then a + sign and another value. Do I just put in a number for the first box and then click the save icon?
Yes, or press the Enter button on your keyboard. They add $.25 on top of your price so a $1.00 card will appear to a collector as $1.25. If your a flipper, you can shop in flip mode and you will see the $1.00 price.