most horses take to herbs naturally.  After all, horses are herbivores and will seek herbs out in the wild.  But, if  your horse has never been exposed to herbs, it is an easy process.  First, put a pinch of the herbs in the palm of your hand.  Let your horse smell, and lick the herbs.  You will be able to tell quite readily if he or she will eat them readily.  If they seem to like them, put about 1/2 the recommended dose on their feed that day. Then, simply increase the amount at each feeding until you are feeding the appropriate amount. If your horse is a finicky eater, and seems to not like the herbs, you can add apple cider vinegar to their food, or honey, or molasses.  Again, start with a small amount, and when the horse is eating them readily, increase.  It is easier to get horses to eat any supplement when sprinkled over sweet feed, since powder sticks to the feed naturally.  If you feed pellets or oats, you may have to wet the feed to get the herbs to stick.  Obviously, no additive will help your horse, if they don't eat them.