How can I change 'choose option' to 'add to cart' functionality in Dawn Theme?

[Aly7]

Hello , I am trying to change the button "choose option" into "add to cart" I am successful only to change the name but the functionality is still the same. When we click on add to cart (only name changed) it's not adding the product to cart. I searched for any snipped or something else on the internet but didn't found anything related to this problem. Any idea how to achieve?? I am using Dawn Theme. Here is the url https://bto.us/ password: 123456

Thanks

[MRamzan]

You can change label by doing this: