Welcome to PC Simulator Save Editor Help. I'll guide you how to use the program.
Most help is also available through tooltips.
First step: Taking a look at the program

The left textbox is where you put your encrypted/decrypted texts to decrypt/encrypt.
The right textbox is where the encrypted/decrypted files get decrypted/encrypted.
Press ENTER on the left textbox to encrypt/decrypt.
File Menu
The Open button opens a save file.
The Save button saves the current output text to a file.
Options Menu
The "Automatically decrypt when opening file" checkbox, if checked, decrypts the save file before outputting it.
The "Automatically encrypt when saving file" checkbox, if checked, encrypts the save file before it then gets saved.