I've downloaded a couple of custom foods for my sims to eat, but whenever I play the game, they are nowhere to be found in the menu. I've checked the cooking skill but still nothing? Any ideas? Pls help!

Go back to the creator's site, read the information provided, see if there's anything you missed or did incorrectly. If it's not showing up for sims who have the cooking skill specified, it's possible you had an error during download or it didn't install correctly; redownload, take out the existing copy, replace it with the new copy. If it still doesn't work as advertised, you'd best talk to the creator.