Airlock or not?
Fermenters come with a lid and a small hole to fit an airlock, which is filled with water and allows CO2 created by the yeast during fermentation to escape, but does not let air into the fermenter.
While there's nothing wrong with using a lid and ailock, many brewers fit plastic food wrap over the fermenter so they don't have to worry about sanitising the lid and because they can see the fermentation more clearly. After bottling, racking or kegging just remove the plastic wrap and throw it away.
To use plastic wrap instead of the lid, remove the rubber seal from inside the lid and use it to secure the food wrap around the neck of the fermenter. There's no need to put any holes in the wrap; the CO2 will find its own way out.