Hi JJHeckt,
Thanks for coming to Apple Support Communities for help today. It appears your Mac Mail app won't open.
Since this sounds like the first time you are using the app and you want to sign into your email, have you tried going through System Preferences > Internet Accounts? It might be worth a shot to enter the information there and see if the Mail app will then launch for you.
Have you checked for any macOS updates? Please see: How to update the software on your Mac then scroll to "How to get updates for earlier macOS versions".
If those steps don't resolve this, try isolating the issue further. Start with booting up into safe mode: Use safe mode to isolate issues with your Mac then try launching the Mail app again. If it works, there could be some third-party software that is preventing it launching.
You can also check to see if it launches in a new test user account. This will isolate the issue to system-wide or your user account: How to test an issue in another user account on your Mac.
Let me know how it goes.
Have a great day!