Installing pan gasket with motor in car

Get everything absolutely clean and grease free (use brake cleaner) and brush on a good coat of Permatex #3 "Aviation Form-A-Gasket" onto both sides of the gasket and any threads that go through into the crankcase. OR, throw the gasket away and glue the pan on with a 3/8" bead of RTV. Don't use RTV with a paper gasket.