Professor Ronen can be found in the Transfiguration Courtyard, near the Astronomy tower. If you’ve just finished speaking with Professor Weasley, you’ll be able to leave her classroom, turn right, and then take your first left to enter the courtyard where Professor Ronen is waiting. Walk up to him and begin the quest by pressing /, starting a cutscene in which he’ll inform you that you’ll have to do some preliminary tasks before you get to learn Reparo.
You’ve got two tasks to do now, both requiring that you find a flying page.
Collect the flying page near the broken statue
This one’s very close to Professor Ronen — turn around after your conversation ends, and you’ll see a Quest Search Area icon up the stairs ahead (1). Stand on the semicircle porch on the water (2) and cast Revelio to reveal the page, then look up and cast Accio to snatch it out of the air – it will be flying in a circle around the columns behind you. Make sure you’ve got the page near the middle of your screen before casting Accio!
Collect the flying page in the Defence Against the Dark Arts Tower
Go back into the courtyard, then turn left and head through the nearby door (1). Continue straight and up the stairs, then cast Revelio while on the stair’s landing (2) — the page you’re looking for will be flying around above you. Once again, aim at the page and cast Accio to retrieve it.
Return to Professor Ronen
After collecting both pages, you can return to Professor Ronen in the Transfiguration Courtyard. Speak with him and he’ll teach you the Reparo charm — learning it works the same as with all the previous spells you learned, though it’s a bit trickier than most since it’s a loop shape you have to guide your wand through. With Reparo, you’ll be able to mend things like broken bridges or statues.
Now that you’ve finished your assignment for Professor Ronen, it’s time to head to Hogsmeade!