Helping students understand that ST Math is a little different from other math games they might have played is a great idea. You can find advice and resources in ST Math Academy in addition to these great tools:
You can use this Guided Introduction Activity to let students learn about ST Math and how it works.
For younger students, you may want to use the JiJi to the Top Digital Book
and/or this video telling of the story.
And don't forget families! Check out How can I introduce my students' families to ST Math?
For schools using Picture Passwords*, you can share this video to introduce students to the picture password:
*If your school is rostered, your students do not use ST Math picture passwords. See How can I tell if my school is rostered and what does that mean? for more information.