When I try to click the green button next, it says "You need to map the required field Meeting Data". I don't know how to proceed.

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!
That means that it can't find a field with the name "Meeting Date" in your Meeting object. Maybe you misspelled it when you created it back in Lab 2a. Easy to fix - just go to Setup > Object Manager > Meeting and then Fields and Relationships and click that field and edit the name & save. Then the import should work.
If you don't have that field at all, you'll need to add it but you probably do or you wouldn't have been able to get to the end of 2a.