How do I get and set digital signatures with the 21 CFR part 11 standards as defined by the Food&Drug Administration of the USA?
Reading the regulations themselves is a big start there. I'd also look at the most recent guidance that I've found. As I quickly interpret it, these aren't digital signatures in the way that most of us are familiar with. Rather, they are fields on data set by a controlled process which requires authentication, creates audit logs, and is under appropriate controls.
I'd implement something like that with a table that links signatures to document ids and records all entries with sequential numbering.
Beyond that, you're probably into needing to pay for consulting work.