On your SD card, create a folder called 'apps' in the root directory (the main directory when you first browse your SD card). Within the apps directory you just created, make a new directory with the name of the program, in your case, 'Savegame-extractor_v2.0'. Then within that directory, you want to copy over the save-extractor_v2.0.dol file from your downloaded file and rename it to boot.dol.
So basically it will look like this (if D: is your SD card)
D:\apps\Savegame-extractor_v2.0\boot.dol
After you have that on the SD card, insert it into your Wii and boot it up. Load up the Homebrew channel and you should see a somewhat generic list of the program. Select it and then it will come to a window asking you to press Reset to extract the save or Power to reset back to the menu. Click Reset to extract, wait and it will come back to this original screen and you'll be done. Hit Power and you'll be back at your Wii menu.
If I missed anything, plz ask. I just did this the other day myself so I figured I was ok to answer. Good luck.