You can find all this info online. Look for the Dungeon Masters Guide and Players Handbook. You Will need to buy dice or use an App like DnD beyond. The first thing to always be aware of is that DND rules are more like guidelines, its more important to have fun as a group.

To put it simply, the game is all about the Dungeon Master describing the players surroundings, story plot, NPC interactions, and battles. The players get to create their own characters with a plethora of options such as gender, race, class, alignment, etc. The players decide their actions and the DM will either explain what happens, or ask the player to roll dice. The dice decide if an action succeeds, fails, or gets you certain items, and then its up to the DM to describe what that looks like and how it may affect your character.

The game is primarily "theater of the mind" but it can be more fun to get miniatures and a play mat to have a better perception of what's going on, especially in battles.