Skyward Sword HD - Stuck without song for the harp

Question

I have recently resumed Skyward Sword on Nintendo Switch and lost my trail in the adventure on how to proceed:

1. I have directed both windmills on Skyloft and therefore raised the tower.
2. I realized I am supposed to play a melody but do not know how. I read to press "up" on the left controller to activate the harp but it only starts dowsing. The 4-point menu only has the eye on it. not harp.
3. When I select the inventory (+) and hover of the harp, it says I need to learn a song to be able to play it.
4. If I talk to the old lady in the temple she tells me I need to go to Skyloft now.
5. Fi also tells me I need to investigate the tower.

How do I activate the harp? Do I need to learn a song? If not, how to activate the

Answer 1

Nevermind. I found the controls in the help menu (right arrow on the left controller and then +) which told me that the X button is the harp....

So, formal solution:

1. You will learn your first "song" only later
2. To activate the harp, press "X".