too late for referral?

i want to unlock my fourth combat slot but it says the three options so i'm trying to see if it is too late for the two referral codes if not then how do i do it?

If you refer 2 others I think it unlocks. Or for Vip? so if you get 2 people to download game and use your pal code, It should unluck. To get your pal code, click the little yellow guy and it says pal code at bottom of screen.

with me, i reached the floor 3 to get slot 4th