Board Game Arena

I just learnt that the card's cost activates when you're offered a choice of any random star, e.g Time Chamber Discharge reward.

So while you are shown the foir different star options to select, you are also offered the option to activate the card.

Thank you @Tamerlayne

How do we use or activate the 'Time' Action card called Generations? (Green card) <--- LOL
It says the costs is to 'swap a random star'? I don't get it.
I've never been given the option to activate it.
Does anybody know how?