Indie defaults to showing prices for 1 adult in Economy class. Look below the cities you entered. After the search options you also see: “1 adult, Economy”. Tap on that and change to the class of service you need. Then tap “ continue” . Depending on your device’s resolution, you may need to scroll up to see this button.
If you choose “Business” / First but there isn’t availability in that class for some flights, it will prompt you which leg is not available in this class. You can then choose to mark that leg as “by land” and just search again that leg in “economy” or switch back to “economy” for the entire trip.