NASA just uploaded a video to take us through what happened before the launch of Artemis. Ten minutes before the launch of Artemis, the space launch system is on the launcher at Kennedy Space Center located in Florida. Three miles from the site are the launch control centers monitoring everything while the launch area is cleared.
Before the launch, the hydrogen and oxygen are filled up, the communications are verified to ready the Artemis to send Orion to moon for the very first time.
The team leader starts the countdown 6 minutes before the launch, and the SLS core stage transition to internal battery occurs 1 and half minute before launch. Sound suppression system is activated and four RS 35 engines are ignited four seconds before the launch. It takes 5 seconds for the engines to reach 100 percent power and about 2 hours later the Orion is near to the moon where it separates from its ICPS and head toward the moon to finish the Artemis mission.
Reference: Artemis 1 by NASA https://www.nasa.gov/artemis-1