All you need is just to be on the Theme Editor:

1. From your Shopify admin, go to Online Store > Themes.
2. In Themes, click the Customize (besides Actions)
3. From the Customize, click the Top Button and navigate to Product Page (Default Product - basically on any Product Page)
   
   
   
4. You'll land on the Product Page (basically just be on any Product Page.
   
   
   
   

Other Useful Information:

Order in the Next to get it By - Removal of Shipping Estimator (Order in the Next to get it by) and More Information about Product Page - Tabs (Features & Options)

How to Change Specific Texts - Change Specific Texts in the Theme

How to Change Specific Colors - Change Specific Colors in the Theme