Product custom field: Add the Text block to the Product main option, then drag it to any position that you wanna show it.
Step
From your admin, click to Online store => Themes => Customize
Select Product template
Add block Product custom field from Product summary section
Click Save
Field Type: Choose between 'text' for inputting text data, or 'upload image' for the option to upload an image file.
Field Name: Assign a placeholder to the text field.
