Once you have the CD4051 SPICE model link downloaded and imported, run this basic simulation to verify functionality.
Texas Instruments manufactures the CD4051B (the 'B' is important—it's the improved version). TI is the most reliable source for SPICE models. cd4051 spice model link
The Last Link
If you are using a simulator that doesn't support PSpice syntax (like some stripped-down versions of Multisim or Tinkercad), you may need to construct the model using primitives. Once you have the CD4051 SPICE model link