PS3 save data is usually locked to the original user's account. To use someone else's save, you may need "resigning" software.
Download your chosen God of War 3 save file (it usually arrives as a .zip or .rar archive).
The save game files are stored in a binary format and are not human-readable. However, we can explore the file structure and content using a hex editor or a specialized tool.
A common tragedy in this story is the dreaded message: "Cannot load game saves that you do not own." . Most PS3 saves are locked to the specific that created them to prevent "trophy cheating".