Before the backup begins, Time Machine will configure the drive you have selected (if necessary), and prepare the files on your main drive to be backed up.

You can monitor the backup's progress in the Time Machine preferences pane of System Preferences.

You may continue using your Mac while the backup is running. The backup will continue even if you close the Time Machine preferences window.

The first backup could take a significant amount of time, depending on how much of your data you chose to exclude and the speed of your backup drive. Subsequent backups will be shorter.

When the backup is finished, a Backup Complete notification will appear on the upper-right side of the screen.