What does it say on the tube? I looked up some of the hairball remedies on amazon and only found one that included directions in the description. That one said to give 1/2" daily.
You take a prescribed amount on your finger and smear it in one quick motion over the cats mouth, You don't have to be overly precise, the cat will lick it off the fur if you miss.
we had to give our cat that stuff once a day
We never really stopped because it was a Persian when we stopped she continued hacking them up I think it's once a day until it stops if your cat has long hair like my Persian did then you will probably end up doing what I had to do