Positioning Images in Layerslider

Hi,

I’m trying to learn how to create a slider using Layerslider and I have imported one of the free ones from their site, the 6 Layer Slider, I think it’s called.

I am trying to replace the images in the slider with my own, but as mine have different sizes, they need to be repositioned. When I select an image and then go to Styles, I enter some pixel values in Top and Left and that works fine. However, it’s supposed to be easier to drag and drop the images in the slider canvas, but this doesn’t seem to be working. When I click on the image in the canvas, it is not selectable. Text layers, however, are selectable.

Any help here would be much appreciated.
Thanks a lot
Teddy