If you're watching a movie, configure the movie playback software to use the HD audio device built into your graphics card, then use the HDMI port to connect with your amplifier, and finally from your amplifier to your display device. It will carry the encoded audio of a movie to your amplifier without a bunch of fuss.
Your other option is to run digital audio from your sound card to your amp, but it doesn't look like your audio on the computer has a digital output on it. If that's the case, that option is out unless you wish to purchase an add-in board audio card that has digital audio out. Once you're running digital audio to your amp from a sound card, you will still have to encode your computer's audio to receive 5.1 on your amplifier, using either Dolby Digital Live or DTS Connect, depending on the format supported by your amplifier. DDL or DTS Connect is a feature you will have to look for on any sound card you wish to purchase, if you need that feature. It's not necessary when watching a movie, as movies are pre-encoded on the disc, but if you wish to play computer games or music with surround sound, you will need to encode them in real-time as the audio is sent to the amplifier.
It varies for each movie playback software program.
Usually, you will open the settings, look at the audio options available to you, and in there you should have a selection between different audio outputs. The audio output on your graphics card will likely have "HD audio" in it's name.
Sorry, unfamiliar with that program, and none of it looks correct to me. Worst case scenario you could disable your on-board sound device through the Device Manager and leave only the HD audio device enabled on the graphics card, and see what options your program presents you with.
Another option would be to change the default audio playback device for Windows to your HD audio device on your graphics card. Most programs will use the default audio device unless otherwise specified.
From the picture, I don't see a HDMI input on the receiver. The problem with optical it can only send 2.1 uncrompressed and anything above that will be compressed. Analog and HDMI can send out uncompressed audio.
The amplifier doesn't need HDMI in as the OP has purchased an audio extractor which deprecates the need. Most soundtracks are not uncompressed, and most folks are not using audio equipment of the fidelity necessary to appreciate the difference.