Making a stop along the way or taking a detour is not a problem with FREE NOW.
Just tap "Edit drop-off" in the bottom left-hand corner, and enter your new drop off information. Your fare will be recalculated and a new quote will be displayed based on the updated details. All you need to do is tap "Confirm new fare" and your drop off address will be successfully changed.
Note - if you are riding in a Private Hire Vehicle and request an extra stop or a detour, the app will automatically calculate your new fixed fare. If the new fare is higher than the original fare, your bank will either create a second pre-authorisation to cover the difference, or cancel the original pre-authorisation and create a new one for the revised amount. This will depend on your bank provider.