Guys, Xavier told you everything you got to do to add your own classes to the button - which is what you've been asking for.
In the backend, go to > Display > Views, choose HikaShop, your template, frontend, then product, and scroll down to open the view "quantity" under "product". (More on that in the documentation.)
Then find the lines containing ADD_TO_WISHLIST, and/or ADD_TO_CART, depending on which button your after, or both. Follow Xavier's example to add your class name(s) to the code, and don't forget the space in front of it.
The software will save a new copy of the file, even if you screw up, you can delete it and start all over (see the trash can after saving? Ha!)
With your classes added, the button should turn into whatever your template is suggesting, or you use your own CSS to make it huge, pink and with flowers around, or just two words without anything: "cart, dammit!"
Have fun! 
(a friendly user, just like you)