Hi, when you go to the academy there's a learning path on how to build an events app: https://gettingstarted.mendixcloud.com/link/path/42
If you are new to Mendix, take a look at the Learning Paths on the Mendix Academy. They take you thought all the basics you need to build your first App.
As for what to put in your Events App, you’d need to speak to whoever has asked you to build the App to get their requirements.
Hope this helps.