Canon EOS 750D Instruction Manual page 199

In Creative Zone modes, you can set the ISO speed by pressing the
<g> button.
With Live View shooting, you cannot set <B> or <M> for the drive
mode.
When you set w (Partial metering) or r (Spot metering), a circle
indicating the metering area will be displayed on the center of the screen.
Exit the setting.
3
Press <0> to finalize the setting and
return to Live View shooting.
You can also select [2] to return to
Live View shooting.
Shooting Function Settings
199