Game question about battles

Hey everyone, i gotta question about the game's battles. When i see the message that i've been attacked by multiple users does this do anything? How do i get rid of it? Do i have to battle all of my rivals? Or will that message pretty much always be there since people are always battling? Is there any way to go into a battle? Or just the person that initiates it gets to go in?

You need to look in the history secton to see who fought you to get rid of the notice.

To battle you need to go in to the battle tab and pick an opponent.