Connect two audio outputs to 1 speaker?

[MatsyLR]

I'm wanting to connect a Computer and a TV audio (3.5mm) to the same speakers.
I have a Y cable with 2 female 1 male but it doesn't work.
Is it possible to do this or?
Connecting the TV to the computer and using Listen to this device is not an option due to static interference (the computer is causing the static but I can't see why or how)

 

[MatsyLR]

The cable I have is like this one
https://www.overclockers.co.uk/sandberg-3.5mm-jack-splitter-cable-cb-001-sb.html

Sound comes out If i connect it to the one labeled with a headphone, but the mic one doesnt'

Came with my headset.
Looking around on....you know where, they have different decriptions, some say its to connect two devices to 1 audio source and some say its to connect 2 audio sources to 1 device.