Hey Smudgkip, welcome to Tapas! It's great to hear that you're embarking on a comic project. It's an exciting thing.
As many here have already said (and I agree with them) you can just jump in and look back later after you have more of a feel for what the process of making pages is like. Your first page will NEVER be your best work, and frankly that's a good thing.
For a bit more specific advice: I suggest starting in a way that shows off the traits of your main cast. For instance, if your main character is shy, perhaps begin with them struggling to talk to someone. Are they violent, heroic, thoughtful, edgy? Show those traits in action!
An introductory scene does a lot of heavy lifting and it can certainly be a struggle to figure out something that will perfectly encapsulate your cast, world, and ideas while hooking new readers, but try not to sweat it too much on your first project. Comic making is a skill best picked up by doing.
Also, regardless of your opinion of this show, this particular video does a great job breaking down a well done introductory scene for a character. I suggest giving it a watch if you can!