Reply To: Change Attribute product page

Hello,

Please try using the below Custom CSS code and paste it to Dashboard >> Theme Settings >> Custom CSS >> Global CSS section:

.onsale.product-label {
  padding: 15px 10px !important;
  border-radius: 35px !important;
}

In this CSS, the border-radius property will make the edges go round and the padding property will make the space adjust in a manner that the label would look circular. You can modify the values of border-radius and padding here according to your choice that best suits you.

Hope this helps !

Best Regards