Create batch file with these commands:
c:\__full_path_to_virtualenv__\Scripts\activate.bat && python __full_path_to_python_script__.py
&& means run command2 if command1 completed successfully.
Then set that batch file as script to run. You don’t need to set any additional arguments in task scheduler (or you can set them in batch file anyway) and can set Start in if script has to read/write from specific directory and uses relative paths.