Hello & Welcome,
Can I assume that you have the current code for the safe?
Let me give you a link to the owner's manual so that you will have that. This is a PDF file that you can save on your computer and print it out. Just right-click on the link and save it to a location where you can find it (like your desktop).
Once you get that document, take a look at page 2 (of the PDF. It says page 1 at the bottom of the page if you print it out) on how to change the codes.
The basics are to use the factory code to be able to program in a new code.
Please let me know how this works out for you or if you have more questions.
Take Care, Greg A.
I appears that there may have been a situation that allowed two experts to post an answer, so please accept Rod's answer if it works for you, instead of mine.