Harry Potter: Quidditch Champions

The Look! Mum Made You a Sweater! achievement can be unlocked almost immediately upon launching the game for the first time. When you begin any of the initial training modes, you will be prompted to create a character for the role you will be training in. As soon as you make any customization to the character, the achievement should unlock!

If you somehow skip the trainings or don’t customize your characters, you can always customize a character later from the menu when looking at your roster/created characters by going to My Team from the main menu and pressing X on any of the characters to customize them. I hope this helps!