[Muhznit]

The highest-quality educational resources you'd give to a child.

It'd start off simple. We'd introduce them to our base-10 numbering system with dots representing numbers, introduce them to the symbols we use to represent them, and from there, we show that there are other species in the universe capable of understanding concepts that will stay the same throughout. No matter where you are, 1 + 1 is always 2. Preferably, we'd build on these concepts as much as possible, until our alien buddies have learned how we do lambda calculus.

Accompanying the math would be a series of pictures depicting human history and global coordinates of such events. It'd end with the arrival of the aliens. Or preferably auto-playing video on a solar-powered device. Remember, these are aliens here, it's practically impossible to teach them our language without them living among us long enough. But if they studied our math first, they'd have a general concept of sequential progression (. .. ... = 1, 2, 3) so they should be able to piece together things.

Finally, we'd provide them with a device on which they can record their understanding of the universe and aspects of their planet to give back to us, a peaceful way of saying "We shared our knowledge with you. Please share yours with us."