Goto: Catalog -> Product -> General

The default will be select- i.e This is not a personalized product.

Personalization Optional “Yes"

On the product page, personalize button is optional. “Add to cart” and “Personalize” button will be available on the product page.

Personalization Optional “No”

On the product page “add to cart” button will be removed and only the “Personalize” button will be available.