In short, yes you can customize the WordPress theme, You can simply go to your WordPress dashboard > Appearance > Themes, Once you click on the Themes link, a page will appear on the dashboard showing the theme that you have installed. Click on the customize option to edit and customize your theme in real-time.

Are WordPress themes fully customizable?

WordPress themes can be customized in several ways depending on the extent to which you are wanting to change your themes look and feel. From powerful theme customization settings built right into the WordPress Customizer, to add-on plugins and real-time CSS Editors like SiteOrigin CSS.

How do I customize my WordPress theme?

On the Customizer panel, you'll find the name of your active theme and the Change button. If you click on that button, then WordPress will display all your installed themes on the right side of the page. To check a particular theme, you need to click on the Live Preview button.