Do you love the characters in HP? Do you want to observe the life of a wizard up close? Do you want to be part of the magical world?
Merlin waved his hand: "For the sake of your sincerity, I'm sure."
So, you received the gift of Merlin, and with a white light, you traveled through time.
Things to know about time travel: The laws of time and space are very complex. Even Merlin cannot guarantee the timing of your appearance in the HP world. The role you will play is random. No matter how you want to contact anyone in HP, remember, no spoilers!