How do you get passed charms class?

Just follow Nearly Headless Nick into the Charms Class and then learn your Lumos spell as per the story line – after you do you are given the quest to collect five Yellow Bricks and place each of them in the middle of the room in the correct shape – using the spell you light up the end of your wand and chase away the Devil’s Snare which is holding the bricks, after which point you can now locate the first YB on the right side next to the benches.

The second YB is right there on the left side of the room – place the two YB's so that you can get to the upper part of the room by jumping on them, and up, which gives you access to where you will find the third YB. This is by the wall with the spider webs so use your spell to chase away the Devil’s Snare to obtain this YB, and then get the fourth YB over by the chest.

The last YB is the one by the bookshelf on the right-hand-side – assemble them as per the game instructions and that completes the quest, at which point you just need to follow the ghost back into the hallway, which will unlock the passage to the Lessons Hallway and, thanks to your new Devil's Snare defeating spell, also leads to unlocking the door to the Potions Classroom, which is sort of the point to this