Floating button
By default, the size button will appear floating on your store.
You can change the position to 'inline' with the text in the Settings page of SmartSize. See image below.
Inline button
You can change the position of the button to appear 'inline' with the text. To do this, simply select on 'inline button' and check the result in your store.
To check the button appears in line, you must open on a product page with one size chart that is in status active (i.e., not draft)
You still cannot see the size button? This can be normal... some themes require you to add it manually. Here is how:
Easy option, supported by most Shopify themes. Can be configured in Customize Theme
Option available to all users, no coding skills required.