I think that I might be able to help you with that...
I can't save these projects that I start as I am still using the trial but, this is where the images folder is located for the example project: http://i.imgur.com/YUmAYDS.png So I assume that your project file will also have that images folder within the created directory.
Just navigate to that folder, place your 'cropped' and exported new eyes images in there and then go back to Spine and as you can see here, it updates, but it it doesn't just click the refresh button which is at the bottom of that part of the interface, just look down and you won't be able to miss it: http://i.imgur.com/D6WTcQ5.png
Once you have the images in there this is the part I think you were stuck with, to get the alternate eyes on the character, just navigate to the 'new' eyes that you just added to the images folder, then you can just click and drag it onto the slot that you want the eyes to be on: http://i.imgur.com/BSgVwT3.png and from there I assume you know how to check the visibility, but if you don't then it's the little white dot that I've got my mouse cursor hovering over, just check that for the eyes to see them and move into place.
Alternatively you could navigate to the image in the interface, select it, then you can see "set parent" at the bottom of the screen, like in this image: http://i.imgur.com/bx57ntF.png once you click that, you will need to click the bone to attach it to, in your instance you will need to select the 'head' bone, and it should pop up and ask if you want to add a 'new' slot or bind it to an existing one, just check the "eyes" slot and it should be added to that, but you may need to position them correctly.
I am not sure if the images folder will be locatable as they are for me right there, but they should in theory be in the folder created by you when you created a new project, that is the only thing that could be in question, everything else I have told you here should directly translate to solving your issue! I hope that this helps and its as step to step as I could make it, I hope the images assist you further. Most of all, hopefully I have answered the questions here for you lol. In any case, happy Spining!! 😛
Kind Regards,
Patrick
