How to Make Changes in Scroll Top button?

In Azure Pro, there are 9 additional options to choose from, for selecting your favorite arrow icon in Scroll Top button.

Go to your WordPress Dashboard, then Appearance >> Customize >> General Settings >> Scroll Top
Select the best Icon from the given options as per your preference and adjust the size of your icon. You can also maintain alignment of your icon.
In Design tab, you can use the customizing options like: Border Type, Color, Padding and Radius of Scroll Top Button

For more general guidance, follow this link here: Scroll Top Customization