OK, and here you must click the notes that you already can play.
When you move the mouse pointer over a note, it must get a blue box around it.
When you then click on it, it must become red and not striked through. If it stays striked through, we have a problem.
Please make red all those notes that you already can play. The last clicked note gets a red border. This means, that it is the "practising note". Later you will only see pieces that contain the practising note. If you succeed to get rid of the red border, you will be awarded with all those pieces that you can play with your notes (you can do this by clicking some note twice that you do not want to play).
You should select at least 5 notes.