I've set up Nodes with Noise and Bump on my main cube shape, and within the same cube shape (new material) I added the same nodes but this time with I added an Image texture so the material can look the same. I saw a tutorial with a MIX shader and diffuse BSDF, but I'm confused how to set it up, or if it's the right shader to use.
Your bump map is set up correctly. If you want to use a subsurface color, you need to give the subsurface a vale that is higher than 0 (although low values generally work best). If your .png image has built in alpha channel, you can do it all in one material. You can connect it like this: