You have two options to explore
1) as suggested Maciej add a human task representing first form just after the start event and assign it to innitiator. When the initiator start the process either do a) first task can go to initiators inbox or b) claim first task for intiator and show the first form to initiator. For next Approve/Reject task at a node to this first human task in case of rejection.
2) If you have form before starting the process and form data is fed into the process then you will have to create human task programatically and assign it to initiator on rejection by approve/Reject task.
First approach is better as you are able to model first human task in the process.