Genesis 1:28

And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.

1. God blessed the man and woman He created. It isn't clear what this means.
2. God commanded the man and woman to produce many offspring.
3. God commanded the man and woman to replenish and subdue the earth. In addition to populating the earth with their offspring, I think replenshing and subduing the earth means to cultivate it, replant after harvesting/cutting, and keep it viable. I think it also means to care for and manage the animals, taming them where possible and useful, ensuring they have adequate and healthful space to multiple and replenish the earth as they were commanded.
4. God is capable of verbal communication with humans.
5. God must have taught the man and the woman a language prior to giving them a commandment, unless He somehow created them with that skill. He may have delegated this to someone else on his staff.
6. Unless these commandments regarding reproduction, and management of the earth's resources only applied to the first man and woman, or have since been revoked, they must still apply.
7. I suppose it's possible that God just issued these commandments and then left the scene, but it seems more reasonable that He would have provided some training for them on these subjects - things like how to deliver a baby (the man would have appreciated that, I'm sure), farming, which plants were edible and which weren't, etc. He may have delegated this to someone else on his staff.