Customizing the elements comprising your Messenger channel's Get Started screen helps you personalize your subscribers' experience
Your Get Started screen shows a few elements you can customize to your liking. Of course, it shows your profile image and cover photo, but you also have room to add any text you like.
Below, for example, you can see an image of Enter Shikari's Get Started screen, including a customized announcement for an album that was yet to be released.
This copy is fetched from the Facebook Page about section. It can be found and edited here on your Facebook Page > About (in the left sidebar) > More Info > About > Edit.
A better way to customize this text, however, is not to change your Page's About text, but having it 'Show a Messenger greeting'. Navigate to your Facebook Page Settings > Messaging and scroll down to Response Assistant > Show a Messenger greeting.
Enable this feature and a text field emerges. You can click on the 'Add Personalization' button to add dynamic text like 'First name' and 'Last name'.