Most of the time when you kill an enemy they will drop a gem that serves as experience in this game. Collect them and level up 10 times in order to unlock this achievement. You'll likely get to this level around 4-6 minutes of your first playthrough. You can track your level from the top right of your screen and the top blue bar serves as your xp progress bar.
As of 10/20/2022: to have achievements unlock the first time you start playing this game you must unlock the achievements and then close and re-open the game. After that first re-open they should unlock normally.