Hi Aiman,
Does configuring "Posts" mean that add an event as activity record to contact's timeline?
If so, default OOB entities such as Event, Event Registration, Sessions couldn't be set to Activity type entity.
However, you could create a custom entity e.g: "Event Activity", add an Event entity lookup field for custom entity,
then set this entity to activity entity as alternative.
1. Define the new custom entity as activity entity and enable it for mobile.
2. Create a lookup field for associated Event
3. Then custom entity will be available in Contact's timeline.
4. Select associated event record(You can add javascript or business rule on form to auto populate)
5. Alternative event activity record display on contact's timeline.
Regards,
Clofly
