You must first obtain the library files from a reliable source. A popular choice is the STM32 Blue Pill Library
You should see the STM32 Blue Pill board appear in the results list. Select it and click to place it on your schematic. 5. Running Your First Simulation proteus library for stm32 install
C:\Program Files (x86)\Labcenter Electronics\Proteus 8 Professional\Data\LIBRARY Hidden Data Path : If not found above, check You must first obtain the library files from
C:\ProgramData\Labcenter Electronics\Proteus 8 Professional\LIBRARY proteus library for stm32 install
STM32 BluePill Library Simulation in Proteus | by Satyam Singh