Keep your fingers slightly curved but firm so that when you press a key your finger does not bend backward at all. Your thumb and pinky fingers especially will want to lie flat, but keep these raised as well.
Try to keep your arms and shoulders relaxed as you play. This will enable you to use more of your entire body while playing and will help you achieve a better sound from the keyboard.
As you press a key, you should feel the weight from your arm transferring down into the key through your fingers.
Although you might think that the position of your fingers doesn’t affect your playing much, the proper form will allow more freedom and nuance in your playing.