when I try to click new to popup a form to add a new meeting attendance record, it just shows this and doesn't show anywhere where I can search meetings.

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!
Well, when you were adding fields to Meeting Attendance, if you went too fast, clicking Next, Next, Save, then those fields got created but didn't get their visibility turned on. Go back into Object Manager > Meeting Attendance > Fields and Relationships and delete the fields you created and redo those steps to create them again but this time click through slowly and let each page load and execute it's code. Then when you get back to 123, you should see the fields to fill in.
Okay and those are the email, address, and created by ones correct?
No it should have Meeting ID, Contact Name and Enthusiasm only. Steps 78-90