Step number one, stay calm. This may seem obvious but rushing into a dangerous situation without a plan can do no one any good.
Step two, call 911
Step three, approach the scene. If it is safe to do so. Do NOT move the victim. Head, back, and neck injuries are common with crashes and you could cause more harm than good.
Step four, reassure the victims. Tell them they’re ok and help is on the way. Ask them not to move. Then wait for help to arrive.
Also, the only time you should ever move a victim is if you have medical training or there is a risk of further danger, such as a fire, explosion, or further crashes.