Gigabyte not starting at all

Question

when i push the button to turn it on all it does is the lightr on the board comes on the green light comes on on the tower and the keyboard dnt work the moniter does not come on the mouse dont work it seems like it doesnt boot or notheing i get noyting out of it i thought it migh5t bve the ram but ive got ddr ram 4oo in it what do i do next