Hi jenniejenn,
Here's a step-by-step for installing the save:
-- Save both files to your desktop without opening either of them.
-- Locate your Art of Murder save game folder (for XP this is in My Documents. If you have Vista you may need to do a file search to locate them.)
-- Note the last numbered save files in your folder, for example save0012.png and save0012.aom.
-- Then renumber the files you saved to your desktop to follow on numerically, for example save0013.png and save0013.aom. (Renumbering is done by clicking twice slowly inside the text box of the file, which makes it editable. Then move the cursor to the save number and edit it.)
-- Move both files across into the folder along with all your other saves.
-- Exit the folder, start up the game as usual and load the new save from the in-game load screen.
You'll need to scroll right back to the beginning of your saves to find the new one.