If you want to show the Save for later button on the product pages, go to the tab Product settings > Single product settings and enable the option Show Save For Later button on single product page.
Here, you can also enter the text for the button to add the product to the save for later list in the field Add button text
and a text for the button to remove the product from the list in the field Remove button text.
You can also use the following shortcode to manually place the Save for later button in the page: yith_wsfl_saveforlater_button.