Apple iSight and most all other cameras you have working on Mac OS X are now shared with Windows virtual machines by default if corresponding option is checked.
They should be available and work fine in Windows without any additional settings. Though if you prefer to keep your cameras separate between macOS/OS X and Windows virtual machine, please go to your virtual machine's configuration to uncheck Share Mac camera with Windows option:
For Parallels Desktop : Hardware -> USB & Bluetooth
For Parallels Desktop Lite: Hardware -> USB