If you go to the link that @mikechristopher has pointed to you can click ‘edit’ to change that text to be anything you like (as you can with any other text on the site in the same way)
To add a link, use Markdown as on the rest of the site.
For example, the first line of the @Discobot welcome message is written like this:
- I’m only a robot, but [our friendly staff](/about) are also here to help if you need to reach a person.