CPR follows this order:
C – Compressions
A – Airway
B – Breathing

We begin with compressions to keep blood moving.
The standard cycle for one rescuer is:
30 compressions followed by 2 breaths (30:2).
If you are not trained in rescue breaths, or do not feel comfortable giving them, perform Hands-Only CPR:
Hands-Only CPR is appropriate for sudden adult collapse. Breaths are especially important for children, infants, drowning victims, choking, or drug overdoses.