VSTO Outlook Add-In use built in forms

Question

I am building a VSTO add in (I know this is old technology but I have been asked for this at work)

I need to use the existing forms to add a custom event and then edit it or delete it. I can programmatically create events and I can also allow the user to create their own events with my subject and body but I need access to the start and end times after they have pressed save so I can send the time/date to my own API.I am unsure of how to do this.

I am working in C#

Any pointers much appreciated