Thanks for the clarification. There are two ways that this can be accomplished. If you simply find that someone is not the parent, but is listed as such, just click on the "edit" link next to the parent that you want to remove.
On the next screen, you can either replace them with the correct parent, or remove them completely. To replace them, in the top part of the page (Replace father/mother for...) you can either enter a WikiTree ID for someone that you've already created a profile for and simply click Add, or you can enter the information for a new profile and click add.
If you need to simply remove the existing parent, go down to the bottom half of the screen (Remove father/mother) and click the remove button.
Hope this helps!