A) how? And an example of a case which used hearday as credible in court?

There are literally thousands upon thousands. The debate comes up constantly. The rule against hearsay has something like two dozen exceptions to it -- situations where a statement is hearsay, but it's deemed credible.

Here's an easy example: A statement made for the purposes of seeking medical treatment. These statements are deemed credible, even though they're hearsay, because we assume that people tell the truth to their doctors, therapists, nurses, etc.

How is this statement not hearsay?

As I explained in the first post of mine that you responded to, the answer is in FRE 801. Prior consistent statements, like the ones Ford made, are literally discussed under a section called "Statements That Are Not Hearsay."