I started my gimp project with two images one of a cat and one of a boat on a lake and this is how i put the two images together. To make the layer mask I right clicked on the image I wanted the layer mask on in this case it was the cat then i added it to the image. I used the layer mask to add the cat sitting in the boat. Originally the cat was sitting on the grass so I needed to erase the grass but unfortunately I could not do this while it was so far away. Then I use the magnify-glass in the top left corner to zoom in and out. This helped me to erase the green close to the cat without erasing the cat itself. I used a paint brush to erase the green. After I was done all that I successfully created a cat in a boat.