Here are the steps you should take to schedule a live lesson in Microsoft Classroom:

1. Create or open a class in Microsoft Classroom
2. Navigate to Classwork settings and tap on Assign Lesson
3. Choose the option to create Live Lesson
4. Add a topic title and description to the lesson
5. Choose the date and time for the lesson to take place
6. Invite students to join the Live Lesson by selecting Names, Classes, or 'Everyone' from the three options
7. Assign materials and any tasks to the students
8. Tap on 'Schedule' to create the lesson.