https://forum-narutoen.oasgames.com/page/show-post-27405-1.html

You dont have to register for cross GNW. You have alternate weeks of cross GNW. This week was regular GNW. I think you have won it. Similarly in other servers of your bracket ther will be a GNW winner. Among these winners the top 8 in overall group power will qualify.directly for next week cross GNW and there is no special registration for it. In case you dont have enough power to make top 8, then you will again have normal GNW(you need to register) again for two more weeks(since cross gnw is alternate weeks). Since you feel your group power is low it would be hard for you to compete in cross GNW. I think you are better off with rank 1 in normal GNW than lower ranks in cross GNW.