Windows 10 I assume. You need to right click the speaker icon at the lower right side of your screen. Open "sound settings", select "input" pick the Realtek option (digital, optical or analog green 3.5mm jack usually), then in the same screen select "output" choose speakers. To configure your speakers for best audio, on the right of that same screen select "sound control panel". Pick your output, you can hit "configure" and setup stereo, 2.1, 5.1, test levels, your mic, all of that is in that area.
To use the AMD audio you would need to connect an HDMI to passthrough an HDTV or monitor with speakers via HDMI. You could also connect an HDMI cable from an unused port on the GPU to an A/V receiver that has an HDMI input for sound that way as well.
"It worked before you broke it!"