How to activate ascendancy points in other char in the same league?

Hi. If i understood well, if i, for example, make the labirint "normal" and gain 2 ascendancy points with a character, i have this step (and 2 ascendancy points) in all other characters in my prophecy league.

How can i activate those points? I have a new character that now is in act 3 (but not completed the labyrint missions), and i don't know how to give him that points

You've misunderstood, I'm afraid. Trial progress is shared between characters, but labyrinth completion is not. You should find that the lab is immediately open to your other characters, but you still have to complete it on them to get your ascendancy points.