Picking good cabbage will give your kimchi a nice, crunchy texture. Fresh cabbage will also give out more water during fermentation. This prevents oxygen from getting into the fermentation crock, which can carry harmful pathogens.
Now that you’ve picked the right cabbage, here is an easy version of Kimchi. Note that you don’t have to get all the measurements exact except for the salt content, which has to be at least 4% of the total weight. If you read my article on fermentation, you will know that salt prevents all the bad things from happening to your ferment.