As minimum number of Directors for a pvt ltd company is two, you should first appoint a new director before filing form 32 of resignation of existing Director.
Follow below procedure:
1) Conduct Board Meeting for appointing of new 'Additional Director' and resignation of exiting director OR Conduct General Meeting for appointing new individual directly as a 'Director' and resignation of existing Director (Take resignation letter for existing director before conducting meeting).
2) File Form 32 for appointment of new Director.
3) File Form 32 for cessation of existing director.