There are protocol modes, which have published inputs & outputs, and are ment to communicate with stuff outside the composition, and there are regular / normal / standalone compositions that can run in Vuo or be exported also as macOS apps (see the video @jmcc shared, but the online manual hasn’t been updated yet if I’m right, but you can search for help in the Vuo Menu Bar, it has a section about exporting compositions).
The “Render Layers To Window” node will create a window for you to display the composition, but for Final Cut you don’t need a window, you need to output your stuff to Final Cut.
So leave that (you can’t connect a window to an image port, that’s why you’re having trouble), and connect the images directly to the published outputimage port.
Here, there are several combined images, so you can use a “Blend Image” node (see screenshot & joined composition below).
I did not test it in Final Cut, and there may be some other changes to make (haven’t played with Final Cut exported compositions yet), but that is a start regarding the main question.