First thing to mention is that SPX does not have any volume data. So whatever is being displayed on that screenshot you provided it is not volume for the ticker symbol loaded on that chart. Given the very small values displayed I also doubt that is volume from any particular ticker symbol at all.
However what you requested was how to display volume as values above the candles. So that's what we'll provide:
plot data = volume;
data.SetPaintingStrategy(PaintingStrategy.VALUES_ABOVE);
When you add this to a new chart study and apply it to the chart the platform will place that on the volume subgraph. So you will need to click and drag that study to the upper subgraph to get it to display on the candles of the price graph. I am including a screenshot so that you can see where the custom study must be moved.
Notice in my screenshot I have selected the ticker symbol SPY, because that is a similar instrument to SPX except that SPY does include volume data.