Windows Update keeps your system up to date and turning the Windows Updates off can leave your machine at risk. However, if you really want to do that simply type Windows Update in the search box and then click on the Windows Update link.

When the Windows Update Control Panel window opens, click Change Settings and after that under Important Updates click on the drop-down menu and choose Never check for updates.

As already mentioned this might leave your computer at risk, so turn off the Automatic Updates only if necessary.