Proteus does not include Arduino boards by default, so you must add them manually. Download Library Files
If you have legitimate access to Proteus 8.9 SP2 Professional, follow this guide to link it with Arduino IDE 1.8: proteus 89 sp2 professional with arduino 18 free upd
Proteus 8.9 SP2 Professional is a widely recognized electronic design automation (EDA) suite that bridges the gap between schematic capture, circuit simulation, and PCB layout. When combined with the Arduino 1.8 library, it becomes a powerful virtual prototyping environment for microcontroller projects. Proteus does not include Arduino boards by default,