Inspiron 24 7459, how do I mute or turn down the volume?

ok so I've got myself a Inspiron 24 7459 which is a lovely computer. I've got no complaints. Just that how the am I supposed to turn down the volume or mute it completely when I'm using it? like when I'm using the computer you know it's easy stuff, but when I plug in my hdmi so that I can play my video game on my pc, it's loud as , you understand? So like I've found one way to fix it and it's to mute my computer entirely but, I've got music coming out of my Bluetooth speakers, I don't want to mute that too man. Btw just so we're clear right, this isn't a pc game I'm talking about, my pc has the option to switch to PC mode or hdmi, I'm playing the Wii u on this thing man.