How do I add 2 different images to "Double Exposure" by Kochubey?

Hi!

First, I wanna thank Kochubey for her genius filters, watercolor especially

I also really like the Double Exposure filter
https://www.filterforge.com/filters/13177.html

However, I have not been able to figure out how to add 2 of my own images. I can add a second image to the built in pre-view images when I click "Image 2".

But I want to change both images, so that I am not using the preview images at all.
I want to upload my own images for imgae 1 and image 2, but there is only a button for image 2.

I have found a thread with examples using 2 new images and not using the built in preview images, so I know it can be done, but there are no instructions on how to upload 2 different images.

https://www.filterforge.com/forum/read.php?TID=13275

all responses are appreciated

Thank you! Got it Seems so obvious now.
(Didn't mean to post in the wrong section.)