so you tried to install manually and your device is in fastboot/bootloader mode? If so I think it is normal that you do not see it in the device manager. Else, are you sure you have a data cable? When you have issues during the manual installation, i.e. there is no device found in fastboot mode you may need to update the driver, this is e.g. explained under prerequisites in the manual installation guide. Or are you already trying to update the driver and there you cannot find Android? I think the step to search for Android in the device manager is not mandatory, here another guide to update the driver.
Edit: in the device manager turn on hidden devices, I think you should find Android under other devices then, no need to have the FP connected . If FP is in fastboot mode and connected and driver are up to date you shoud find under Kedacom USB Devices-Android Booloader Interface.