HR Renewel: Updating infotype using FPM based Process and form

Hi Experts,

I am new to process and forms and I need to create a form having few fields to be entered by user and after clicking save button, it should save the record in the time infotype.

I have created the form and process and  but i am not able to figure out the place where I can place the custom code for SAVE buttom.

I have created the User-event and field group but I am not sure how I can access these fields and where to write code for SAVE event.

Kindly share the steps or blogs which can help me to understand the FPM process and form.

Thanks,

Shilpa.