Props to the employee for wanting to understand how to manage and lead people.
I've not found the SHRM to be helpful in employee development. This site is very helpful, though, and has good content but a goofy name: Leadership courses
If they're really interested in developing their management and leadership skills, this course from U of Michigan on Coursera looks very good for new managers: Leading People and Teams
Udemy has several courses for managers: Management skills
Also, check out some courses from SkillPath: Management and Supervision
The HBR series is very helpful and often free: Harvard Business Review - New Managers
I hope these help and good luck to the new manager!