Build an Interactive Story App - I can`t access the drawables that I have downloaded using src from properties?

I downloaded the mars_drawables files from the teachers notes, then I put them in the drawable section by right clicking on drawable > Show in Explorer (on windows), then copy pasted the files into the drawable folder. When I click the drawable folder under the project tree, it shows that the images in all of the resolutions are all there. However, when trying to access these through imageView > properties > src > Project > Drawable, there is only a picture of a file with a question mark on it, and when I click on it it assigns @drawable/ to the src, which I think is just a reference to nothing being there. How do I get the View to be able to recognize the images? Any answers are much appreciated.