Help me tell time!

I got my motor in the car and ready to fire up. I made sure to make the distributor point toward the number one cylinder. I have a timing light and was curious is the next step is just to turn the key and start timing while it's running or do I do something else
Before firing it up.

Also I have never used a timing light and actually timed a motor. What exactly do I do?

360 .30 over
Mp .484 cam
Aluminum heads
Flat top pistons.

If I need more details just let me know and sorry for the ignorance!