I am trying to make my artwork that when I place it, it will snap to artboard and taking the whole artboard size. I tried to use a script that will fit my artwork to my artboard but it seems changing the scale of my photo making it smaller, see the attached photo. My purpose is when I place the photo shown in the middle of my artboard it will snap to the entire artboard without changing the size of that triangle in the middle. That's one photo by the way I just highlighted the rectangle object in my photo/artwork.
It will distort the image if your artboard and artwork aren't the same ratio.
You turn on Smart Guides (Ctrl+U) and then while holding down Shift you can drag the corners until it's just about the right size.
You can also scale down the artboard with the Artboard Tool (Ctrl+O) to fit around the image.
If you do need that size and ratio artboard, you can open the image in Photoshop and then set the ratio and crop it as desired, then load it back into Illustrator