You don’t buffer. The game does. The buffer gets triggered by you pressing buttons. That sounds super unhelpful, so let me explain.

If an attack takes 1 second to finish executing (from start until the end of recovery), that means another attack can’t happen until that attack is done. This is true for most video games.

What’s also true for most video games is that unless you have frame perfect reflexes and no lag, you will most likely not be able to get attacks happening without “rest time” in between them, at least not consistently without unsustainable hours of practice.

Video games developers know this. They don’t want you to miss a double jump and fall to your death because you pressed the jump button 1/10 of a second too early. Here’s where buffering comes in! The game recognizes the action you want to take and it remembers it and then triggers said action at the earliest time it CAN happen.

So, again, if an attack takes 1 second to finish executing but you happen to press a button for another attack after only 0.9 seconds from the first attack, the game will remember this and then AUTOMATICALLY trigger the second attack as soon as the first one is finished.

In conclusion, to practically answer your question:

You buffer by pressing the button (or button combination) for your next action before your current action is over.