Android : Need help creating a line graph with MPAndroidChart

I am using this library MPAndroidChart and I can't understand it much, I want to make a graph like this

Right now I have this

And this is my code:

private void setData(float range) {
    ArrayList<String> xVals = new ArrayList<String>();
    String[] nikotin = { "100", "75", "50", "25", "0" };
    for (int i = 10; i > 0; i--) {
        xVals.add((i) + "");
    }
    ArrayList<Entry> yVals = new ArrayList<Entry>();
    for (int i = 0; i < 5; i++) {
        yVals.add(new Entry(i, i));
    }
    // create a dataset and give it a type
    LineDataSet set1 = new LineDataSet(yVals, "Nicotine Lowered");
    set1.setColor(Color.BLACK);
    set1.setCircleColor(Color.BLACK);
    set1.setLineWidth(1f);
    set1.setFillAlpha(65);
    set1.setFillColor(Color.BLACK);
    ArrayList<LineDataSet> dataSets = new ArrayList<LineDataSet>();
    dataSets.add(set1); // add the datasets
    // create a data object with the datasets
    LineData data = new LineData(nikotin, dataSets);
    // set data
    chart.setData(data);
}

What do I need to change?