If it's a .RAR file, or any loose file, you can still unpack it, and create a folder on your USB in your PS4 folder with a "dummy" account number (combination of letters and numbers, maybe even just the same number of 0's as are in a regular account number which you can check if the USB has any save data from your PS4). Put the files in the dummy folder like so: "[drive]:\PS4\SAVEDATA\0000000000000000\" [or whatever you chose]. Instead of using the import function, Savewizard will read that dummy folder as if it's an actual account, and in the resign menu you can open up the game name, and I think right-click the save data (with the dummy account listed next to it) and resign it to your profile. I've tested this many times with several games.