Press the button with the combination of tones you hear. For example 1 + 1, if your selection is right, play another. You can press Repeat.
With the buttons with the IPA transcription you can hear the associated combination, observe the sounds.
The figure shows you the graph of the sound you are listening to, the blue lines are the frequency variations. Pressing the buttons with the IPA transcript shows you another figure with the graph of the sound corresponding to the button you pressed. IT IS VERY IMPORTANT THAT YOU NOTE THAT ALTHOUGH THE PINYIN USES THE WESTERN ALPHABET THE SOUNDS THEY REPRESENT ARE NOT THOSE OF YOUR LANGUAGE.