I'd like to add on a bit to the (excellent) response by
@William55401. First, to be clear, validation won't
make it compliant; validation can only demonstrate compliance. You can effectively glean the requirements from the
regulation and demonstrate compliance as part of validation using the previously-indicated guidance.
It sounds like this is a home-grown system and, to be frank, if the developers didn't consider Part 11 in the design, it's pretty unlikely that you can demonstrate compliance. It's not something you can just bolt on.