In the tutorial below I show how you can add this under the Classwork section as material (as well as add the topic of Contact Information).
In the tutorial I also show two ways you can add your voice directly into your classroom. This would be extremely beneficial if you need to clarify any directions, or you just want to say hi to your students!
In the past I have used the Talk and Comment Extension (see blog post); however, sometimes your voice may be a bit lower than normal. If this is the case I recommend using the website Online Voice Recorder, upload to Drive, and share the link (remember to check sharing settings).
Embedded below is a 1 minute and 56 second YouTube tutorial.