Select boanding then a monster, then use item and choose, I think you mean that
you need to unlock the royal army, then you go to an enemy territory and click invade (check the skill tree)
Master Nono has a patreon
https://www.patreon.com/nonoplayer
This month there should be an update
I don't know what they're complaining about, the game is beautiful, the scenes are incredible and the story is interesting
Very good job Master Nono and company10/10