Here's the official download link for the Proteus Arduino simulator. You can either try the tool for free or purchase it to enjoy the full features.

Download the Arduino Proteus Library from a trusted source. You can search for "Arduino Proteus Library zip" online. The file will usually be in a .zip format. Extract it to get the .IDX, .LIB, and ...

After cloning the idx and library file, copy it and paste it in the library folder of proteus (which can be found in Programs/ (x86) file).