It's simple and easy, just play around with color and size options in the marks shelf.
All the customization tools are available in the marks shelf,
To Customize the label, click on the Text shelf and click on the Automatic and choose an appropriate alignment.
To customize the size of marks, click on size and slide across the slider to increase or decrease the marks in the visual.
You can also change the marks in the visual from automatic to marks and shapes as per requirement using shapes shelf.
Hope this helps you.