How to create a custom input and expose it to upload images (decal filter)

Hello, 

I created a decal to use in a 3d software called Vstitcher, this one has a full integration with substance sbsar files. I took the idea of creating this decal from a file from the Substance library (attatched), as you can see in the screenshots this sbsar decal loads perfectly into vstitcher and you can even upload custom images to create different masks/shapes with it. I wanted to create a decal to use like so in vstitcher as well, so I did. The problem is that I don't know how to expose the input to upload the custom images so this can be seen and used in vstitcher. I tried copying the same input node from the substance library file and pasted it into mine, but that didn't work. In the screenshot of my custom decal, you can see that I tried by adding 2 times the copied input and one time a regular input, to see if either of them worked, but no. What do I have to to to expose this input so I can upload custom images inside vstitcher like you do with the decal from substance library? The only difference in functionality between my decal and substance's is that mine is not a mask, is a starter shape. 

I would really appreciate your help, thank you!