in the shop for the battle dolls there's always a "Battle Doll Bag" item that's first in the selection that you can buy for 1 coin or w/ehow to use the battle dolls.... i bought a few but i dont see an option on how to activate them
you buy that, buy the dolls you want, then go to your key item menu and use the appropriate bag and it'll open up a selection where you activate/deactivate the dolls