New Build Black Screen

Well from my earlier posts i was making a gmaing pc. this is my 1st build so i could of missed something out but i turn it on, green light on mobo fans go spinning. but nothing else. tried 2 montiors, going back inside to check if something isnt plugged in. i have 1 wire left from the motherboard box the fat plastic wire but i dont know where to plug this in? the hardrive has power and a sata smaller cable plugged in do i need to put this fat one aswel? do i need a hardrive to boot bios?
basically my monitors dont receive anything. any help would be great as im kinda gutted i hit a wall.

nevermind i forgot to plug in the 4pin power plug.