First, WikiTree only allows one set of parents to be connected to you. Your choice is:
a) stay connected to the family you grew up with, but edit your father to mark him as non-biological. There are check boxes for that on your edit page, on the right-hand side where it lists your parents.
b) change your father to your actual biological one. I think WikiTree prefers showing biological parents, but doesn't require it. Again, on your edit page, you would click the [remove/replace father] link to connect to your bio-father.
Either way, you might want to explain the circumstances, and indicate the other father, in your biography.
Hope that helps.