Everytime I go to "User Management Settings" this screen comes up. It's not allowing me to reset the passwords so that I can act as Riley and open the email message.

Sorry you're stuck but there's almost always a pretty easy fix! Do NOT try to start all over again, uninstall Max's Pitch Package, etc. That can make it worse. There's a 95% chance the same snag/fix is listed & answered in the Help FAQ. But if you can't find it there, post your problem here.
Make sure you post in the right category below & be sure to include a screencap showing the issue!
Did you not create Riley as a user in Lab 3a? For now, got to those steps in 3a and create Riley as a user. Then you don’t even need to do the part reset part anyway. You can just go on with 3b at that point.
You're not supposed to go to User Management Settings. The instruction says "just BELOW User Management Settings":
On the lefthand side, under ADMINISTRATION, click Users and then find & click Users under
that (just below User Management Settings)