when apu is running, turn on left engine starter, the knob is on the OH panel to the right. make sure the fuel pumps are running (6 buttins in the center of the OH panel, other 2 are for xfeed). engine should start up and ignite automatically, self sustaining idle state on N1 ~45%, repeat for eng 2 and enable both engine generators. then turn off apu and batt
TURN OFF STARTERS after start-up!
edit: enable hydraulic pumps too, the buttons (4, 2 for gear and 2 for flaps, spoilers) are to the left.