What should I do in the yearly group event?
Just talk to your colleagues, ask them to show you their previous presentations. It's perfectly fine to be afraid to make a mistake and ask "silly" questions.

Here's what I would do: tell about your previous research, if you are from different country/uni - maybe show some pictures. Then tell about your project - even if you don't have any results (and it's ok) you can talk about your research plan, experiments you plan to do. It's good to have feedback/suggestions from seniors at this stage.

Then, if you're new - you can introduce yourself to others, maybe have one slide with pictures that represent your hobbies, etc.