How to correctly create a context map (ddd event storming and Impact Mapping)?

Question

Software design

Hello! I want to make a design scheme of contexts. Their interaction. Please tell me where to start. How and where to design a visual scheme. Here, probably, Miro will do. But what matters most is how to do it right. I will be very glad if you help me with detailed answers, some examples.

The visual scheme will help to understand the architecture of my contexts.

It would not be bad to describe something with a real example. I want to describe several contexts:
Authentication, Events, Event Registration, Event Results, Geo.

Authentication - serves for user authentication, password recovery.
Poster - serves to publish various types of events of various types: competitions, camps, battles, contests, championships, and so on.
Registration - serves to manage applications for events of various types, calculate the cost of participation, calculate awards, and scheduling.
Results - serves to calculate the results of different types.
Geo - serves to store information about cities, countries and regions.

Another design question. A Person can be used in all of these contexts except GEO. Does it still make sense for me to create a Person context ?

For example:
In events he is: Organizer, volunteer, security guard, host.
In registration he is: participant, mentor
In results he is: participant, judge, presenter, mentor

As you can see, they strongly interact in contexts. But such a division is isolated by the fact that the results can be considered on a third-party resource.

The second most important nuance is that mentors can add participants. Participants may not initially have an account, then how to make a connection in this case? Through a link table? ID doesn't always work. Since the participant may not register himself.