Where you write the address, there is a button to find the address (so that the system gets the coordinates for it from a system).
Maybe you did not notice it, or “find address” is ambiguous? Would appreciate to understand where the user experience problem is and improve on it.
In any case, even if a user forgets to use it, group administrators can edit the post and click on find address to get the event to the map. I would therefore not see that as a blocker for its’ further usage, but definitely as something to improve in the user experience.