It really depends on where you are currently at in the legal process.
If you have not yet plead Guilty to the judge and been sentenced then you probably still can change your plea to Not Guilty.
If you have already plead Guilty and been sentenced, then you must file an Appeal. There are time limits for filing an appeal, normally within about 30 days from when you were sentenced.
In your appeal you need to list every reason you have for asking the court
to overturn your plea and let you now plead Not Guilty. You said that you feel that something was misrepresented to you, and that this misrepresentation caused you to plead guilty? Make sure that you include every tiny detail about that misrepresentation: who said it, what you thought it meant, how it made you decide to plead Guilty, and how exactly is was misleading you.
This appeal must be in writing and given to the court as well as the prosecutor who had your case originally.
I would suggest that you get a lawyer to help you with this. If your lawyer was the one who misrepresented to you, then you need to hire a new lawyer to help you with this appeal.