I wanted to restore the data on my PSN account on another PS3 to the PS3 I am using now. How is it done? Also I have two more accounts and I don't want to disturb them or delete their data.
You cannot transfer all data to a PS3 system you are currently using because when you perform a transfer it deletes everything on the destination system, including the other accounts you don't want to disturb.
Game saves can be transfered without erasing the second PS3. To do that you'll need to sign up for the Playstation Plus service and upload all your saves to the cloud using the Save Data Management, then log in on your second PS3 and download those saves.