I'm totally lost (adding Canvas image)

So I wanted to create a fade screen between scenes. I’ve got the game moving between scenes no problem but then i try to add a UI > canvas > image and i get this.

The tiny box in the middle is my current game area (displayed right with placeholder images)
the size of the canvas/image added is just ridiculous and I cant change it. It’s like 500 times bigger than the screen res.
posx 386.6355 posy 333.7162?
Are these just arbitrary numbers? They aren’t editable. Why not 0,0 with an editable width/height?
Where did width 772 come from? My game resolution certainly isn’t set to that and the box it’s added is more like 80000 width.

Ok, I figured out I need to parent the canvas/image to the camera (doh)
Just need to sort out referencing the ui object so i can change the alpha transparency.