This is an accepted solution.
Hello @Helina !
You can change Add to cart button to buy now
by from following these steps:
From your Shopify Admin, in the ONLINE STORE channel, click THEMES.
Select the [ ... ] button on the top-right corner and select EDIT LANGUAGE.
Click on the PRODUCTS tab, and change the text in the "Add to cart" field to "Buy now"
Then click SAVE, and you're done!
Hope this helps!