Find the export button, right below the save button. Make sure you're on the PNG tab. Then, click the very last download button, under "Selected Frame Export."
Click on your second frame on the left. Find the export button, and make sure you're on the PNG tab. Then, click the very last download button, under "Selected Frame Export."
Move to the cat's costumes tab. Put your mouse over the costumes library in the bottom left corner, and click on the "Upload" icon that pops up. You will need to navigate to find your frames. Try searching for the name of your file (which was something like "Blob Walk.") Do this twice, for both of your frames.