Miracast not available?

Miracast has nothing to do with audio, it's used for wireless display. It has specific hardware/driver requirements.

More info here:

http://www.tenforums.com/tutorials/53814-connect-wireless-display-miracast-windows-10-a.html

Regarding your wireless speaker, it doesn't use the same wireless technology (WiFi) that your laptop uses to connect to a wireless network. The wireless system your speaker uses is not compatible with your laptop's WiFi.

If the speaker uses Bluetooth and your laptop has Bluetooth built-in, it should work provided you enable Bluetooth on your laptop and you "pair" it with the speaker. If your laptop doesn't have BT built-in, you can buy a BT USB adapter.

If the speaker uses some other type of wireless technology (as used on some keyboards & mice) it should have been supplied with a matching USB wireless receiver to plug in to your laptop.