"We won't stand for plagiarism..."
That's from this site's own rules.
I've sent an e-mail to ficwad admins.
It doesn't matter what your intentions were, it's still plagiarism.
Also, don't lie. You posted this with every intention of claiming it as yours. The only reason you've admitted that it is not your work is that someone called you out. Otherwise, you would have mentioned the original author's name in the posted chapters. And we can still see the original description on your bio page:
"Harry gets a new book and uses it to his advantage, along wit a number of others."
It doesn't mention "I didn't write this."
As I stated before, I've contacted the admins. Do us a favor and man-up. Admit you were wrong to post another person's work, regardless of the reasons, and delete this fic.