On this page of the Assassin's Creed Valhalla guide, you'll find a detailed walkthrough of the Dearly Bee-Loved side quest.
Reward for completing the mission: 1200 XP.
In the place marked in the picture above, you will meet a man named Gill. From the conversation with him, you will learn that he is troubled - a witch has foretold him that he will be killed by the sting of a hairy demon. A man has written a love letter but is afraid to deliver it because his love breeds bees.
Eivor will take the letter from the man and say he will deliver it for him. Jump off the wall and walk to the flowery meadow. We have marked the correct addressee of the letter in the picture above.
Hand the beekeeper the letter, then follow him. The men will meet and talk, and the mission will end.