Here's a quick tutorial on how to use locked game saves on your CFW PS3.

What you need:
FTP application on both your PC and PS3 or a file manager.
A locked game save.
What to do:

1. Open up your FTP program or a file manager.
2. Go to "dev_hdd0/home/0000000x/savedata".
3. Copy the locked game save to the "savedata" folder so it should look something like this" "dev_hdd0/home/0000000x/savedata/BLES12345-B0".

If you're on OFW and wanted the locked save file to have the same user ID as your other save files and also unlock the save you can use PS3SaveUnlocker.

Here's another quick tutorial on how to use PS3SaveUnlocker.

1. Load one of your own Param.sfo files from another save file you own in the "your Param.SFO" option.
2. Load the Param.sfo file from the save you want to unlock.
3. It will make a new Param.sfo file, copy that to the save file you're going to use.