Ideally, you should enrol in a recognised first aid course so you can learn techniques such as cardio-pulmonary resuscitation (CPR) and mouth-to-mouth resuscitation under proper supervision. This will make you confident and capable of using first aid if you have to.
If a victim has spinal injuries, moving them may only worsen their injuries. You should never move a collision victim unless it is absolutely necessary.
The only instances where you should move someone before medical help arrives are when
The person is trapped in a vehicle that is on fire or in danger of catching fire
it is necessary to move them to:
give mouth-to-mouth resuscitation
stop severe bleeding.
If the patient is bleeding badly, you should try to stop or reduce the bleeding:
Raise the part of the body that is bleeding. This will take some of the blood away from the wound.
Apply pressure to the wound, preferably with thick, folded fabric, such as a towel or an item of clothing.