I'm at 3. I don't know what to do next
What is ???
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is there a different way to access the save file?
Tinkering with the Registry Editor is the only way to access the save data for this game.
What are you trying to do? Make a backup of your saves, or apply someone else's saves?
If you're making a backup of your saves, you right-click on "Something Unlimited" in the Registry Editor and click "Export", then choose a location to save it. This creates a .reg file.
To apply save data from a .reg file, you just need to double-click the file and then click "Yes". Bear in mind that this will overwrite all 3 save slots in your game.
(Also, if you're suspicious of .reg files you've downloaded from the internet you can open them in a text editor such as Notepad to see exactly what Registry entries they edit.)