[OneShot]

I just purchased a used PPK/S and fired it for the first time yesterday.  It misfired several times due to firing pin not striking the primer hard enough.  The firing pin appears ok, protrudes 1//4+ inch from bolt when pressed from the rear. I assume it just needs cleaning.  How do I take down the weapon?  I pulled down on trigger guard, then what?   Thanks for any help.