Pokémon Mystery Dungeon: Blue Rescue Team and Red Rescue Team/Gameplay

Butterfree comes up explaining that her baby has fallen down a fissure and that there are angry Pokémon down there. You and your partner go to investigate.

Enemies can appear anywhere at any time, but unlike most Pokémon games you can see them before they attack. Press to attack. Note that both you and your enemies can attack on diagonals.

On your way you'll find some Poké, the currency of this game. Eventually you'll find some stairs. Step on them and choose Proceed to advance to Tiny Woods B2F.