I haven't done these steps yet but I keep getting an error that's not letting me go on. Am I doing something wrong?

Sorry you're stuck but there's almost always a pretty easy fix! Do NOT try to start all over again, eg. uninstall Max's Pitch Package, etc. That can make things worse.
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Before you post make sure you check the Help FAQ for an instant solution first. Then, if you can't find it there, you can post your problem here and we'll get to it ASAP (within 24 hours), but be sure you:
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post in the right category
INCLUDE AT LEAST ONE SCREENCAP IN YOUR POST TO SHOW THE PROBLEM!!!!!!!!
explain the problem clearly
Well, if it's telling you that, you must have already created the Pitch field in Meeting. If you go to Setup > Object Manager > Meeting and then click on Fields & Relationships. I'm pretty sure you'll see Pitch is already there. You must have completed those steps somehow already. Go ahead and post a screencap of the list of fields if you want and I can tell whether it's been created correctly.