How to have elements pop into screen

I started vtubing a while ago and am in the process of making my stream more interactive. I really like how this creator has it set up so a little camera overlay slides in with a sound effect so she can show pictures on stream, does anyone know how to make elements slide in like that?

Video should be timestamped, but it starts at 20:00

https://www.youtube.com/live/2NivruleQyU?si=B1Y7nf1XKj7lkGSO&t=1205