Clipping Masks

Hello, 

I'm fairly new to indesign and am taking a class for it in college. however my teacher is wanting us to bring in two images and layer them on top of each other and apply effects to the top image in order to give the other image texture. The teacher is wanting us to apply a clipping mask so the top image (regardless of size) will only be applied to the bottom image. I tried to ask for guidance and his response was that if I could figure it out I would get extra credit. I have scoured google and the only way that I can find on how to do this would be to insert the first image (sizing it appropriatly) then make a shape the exact size of the first image and inset the second image into that. Is there any other way that I am missing?? 

I know that I could size the texture image to the same size as the first image, but I think the point is that if you have an image where you can't size it appropriatly you could just clip it down to the right size. I just want to make sure that I'm doing it correctly and that there isn't any other ways that I don't know about. Or if there are other ways, how to properly do them.