need some sr20 coolant help

[nissansr240sx]

ok so i connected my turbo lines, and chose the top of two holes on the block for the coolant feed. so i go to put in coolant, and it spills out the bottom one. so i disconnected the top one and plugged up the bottom hole, and coolant shot out of the top hole. so which one should i use? does it matter? and does the other one do something else i'm not aware of? heres a pic of the area i'm talking about: