Make sure you select "Fight" first! You'll see the Giratina icon pop up. Then, press Z (or Shift, depending on what your keybinds are, but default is Z)
Viewing post in possesing pokemon - Z not doing anything?
thanks for answering. ive found that there even is an indicator to press shift but it only shows for me in raid battles where i cant posses them instead of normal battles. feels like it should be the otherway arround. just wanted to let you know.
so far im really enjoying the difficulty of this game, i hope you keep on working on it!