Merge Three Objects

As Chris mentioned, blending mode might be a good choice, especially lighten. Along with icing  layer masks to get rid of unwanted bleed thoughs. Just use the move tool to position there you want the irises. 

Hello ​@DriftlessPhotographer ,

Can you give us a any history on your experience level with photoshop? Do you have any specific questions or looking for advice about the process? What techniques that you are struggling with to achieve this? Photoshop users will all give you different answers on how to approach this. If you happen to need some tutorials on what will help with this, you can check these here: