Please help how do I enable the tap to click on my computer. It got turned off somehow

What do you mean 'tap to click' ? Are you referring to the mouse ? Is it wireless or does it have a battery if this is what you are referring to.

Have you actually disabled the touchpad.
We'll need to know the make and model to be able to help further.

http://acer--uk.custhelp.com/app/answers/detail/a_id/8086/~/how-to-enable-the-tap-to-click-function