Use your finger or a spudger to press and connect the battery press connector onto the logic board.

This is a good point to test your repair before sealing up your iPhone. Power on your iPhone and make sure it works as expected. Power it back down and continue reassembly.

If your iPhone doesn't turn on, connect it to a power source and try again.

If you've replaced the logic board and the screen fails to turn on, you'll need to follow the screen guide to manually connect the display connector.