homemade co2

i see people talking about co2 how do i make my own? and how do i use it ?
someone told me to get some and cover my plant with a bag fill it with co2 and leave it for a day, does that really work or will i end up killing the plants?thanks ahead of time for your help.

Get a water bottle fill it up about half way with water then put a bunch of active dry yeast and sugar in it then poke a hole in the cap and shake the bottle up whenever you want to give it a boost of co2