in ps2, u press enter so i guess try white or black button for xbox

I have PS2 but I am pretty sure that for both systems you have to hit Start on them. Unless you already tried that, then I dont know. Hope that helps.

for xbox hit the start button and (black button lets you select arena you play on host does this) Up on scorpion with start is random char pick for player 1 and for player 2 its up and start on sub-zero.