Dropping an AP class especially in a core subject is not something you should take lightly. IMO if you can get even a C in the class you would be better off keeping it.
If you want to consider dropping the class this is what you need to do:
–For colleges you have been accepted to:
You would need to contact admissions for each college and find out if your acceptance will still be valid if you drop the class. Do this before you drop the class. If the answer is yes the acceptance is still valid be sure to get it in writing. (FWIW my friend’s D was accepted ED to a competitive college and asked if she could drop down from AP Calc to honors calc and was told that if she did so her offer of admission would be “reviewed” She got a tutor and kept the AP class.)
–If you have any applications still outstanding:
You would need to notify admissions of the change to your schedule. I would strongly recommend doing so in writing.