Use Font-Awesome 4 icons in theme but keep FA5?

[Chaboi_3000]

Ok, I created a png sprite file, but I do I use that in my theme for api.replaceIcon('shield-alt', 'icons-sprite') ?:

or just

For the second image, it’s name is icons-sprite.png, and I want to use that for api.replaceIcon. How would I use it?