Easy!
Have you saved food from a restaurant / cafe / bakery? Show your order in the app to the staff and you will receive the food you have purchased. Then click in the app that you have recieved the food.
Have you saved food from a grocery store? In most grocery stores, Karma food is picked up in the deli counter. In some, the food is picked up in a pink Karma fridge. Ask the staff if you are unsure!
Have you saved food from a hotel? In most hotels, Karma food is picked up in the hotel restaurant, the hotel staff will show you to the right place!