Sorry for the delayed response. That is something quite simple actually.
On page two make a 'conditional branch' make it require 'item in inventory' of the item needed. If it is there, give the reward, add a switch or whatever you need to do to tie up the quest, on the else put you do not have the item needed. Allow me to post an example.
Conditional Branch Page 4
-Item 0001: Quest Reward is in inventory
- Text: Congratulations, here is your reward
- Change gold: +500
- Remove item: 0001: Quest Reward
- Control Switch: 0001: Reward ON
- Text: You do not have Quest Reward, please keep looking.
I hope that made sense, it's hard to show an event without a screen shot, but I don't think it's really needed.