This one is easy, you just need to unlock it
There are so many sidequests in Hogwarts Legacy, some of them chain off each other, and don’t even appear until you’ve fulfilled the proper requirements. Beeting a Curse is one of those quests. Here’s how to unlock it, and complete it.

Step 1: Unlock the quest by playing Summoner’s Court
Take the sidequest Summoner’s Court: Match 1 (after the Map Chamber quest), and defeat Leander Prewett.
Afterward, you’ll be able to take on the “Beeting a Curse” sidequest from Samantha Dale.
Step 2: Speak to Samantha Dale at the Greenhouse
Talk to Samantha Dale to get the rundown of where you’ll need to go next.
The game will provide a marker for the tomb in question, and it’s fairly close.
Step 3: Go to the Dale Family Tomb southeast of Hogwarts
Head into the Dale Family Tomb southeast of Hogwarts (pictured above).
After entering the tomb, turn left and cast Confringo/Incendio on the vines (or just use Lumos) and slide down the chute. You’ll square off against a Troll enemy (more tips on how to beat every type of Troll here): defeat them, and continue down the path. Interact with the tomb, and you’re good to go!
Note that this tomb is part of the “Intrepid Explorer” achievement/trophy, which tasks you with discovering all cairn dungeons.
Step 4: Return to Samantha Dale at Hogwarts
Go back out the way you came, then look up to the left. Climb up the platform and enter the little hole in the wall: this is how you’ll exit the tomb (since the chute is a one-way slide).
Go back to Samantha Dale at Hogwarts (their position may shift slightly, but it’s still the same Floo Flame spot) and turn in the quest. That’s it!