The Beehive is available to purchase for 2,500 coins from the game’s shop. Once you purchase it, you can basically leave it alone. So long as you have Alfalfa that is ready to harvest on your farm, the bees will leave the hive long enough to pollinate the Alfalfa flowers, and create one jar of honey for every square of Alfalfa they pollinate. Grow a whole field of Alfalfa for your cows to turn into milk, and you’ll receive profits from the bees by default, at a rate of 5 coins per jar.
The pollination by the bees does nothing to affect the Alfalfa itself, which can still be harvested as normal and fed to your cow, to produce milk as usual.
Head over to the game’s page to purchase a Hive for your own ranch.