How can I resize one layer to fit another?

[dblj]

I am trying to do this project where I take a photo of my face every day, and I want to stabilize my photos using GIMP. In my first picture, my face is more zoomed out than in the photo I want to edit, so I want to shrink the photo I am editing to fit that. How can I change the size of a layer? 

Similar to this instance of this video: https://youtu.be/FGXGHYonfGM?t=178