Hi @J_D, and welcome to the ODK forum!
Could you tell us more about the actions you took immediately before the issue arose? Did you upload the form XML to Central within your web browser? What happened next?
ODK Central does not require that the form reference a project. A project can contain multiple forms, and you can upload the same form to different projects. You shouldn't need to specify the project name in the XLSForm, and as far as I know, there's no designated place in the XLSForm to do so. You mentioned that your XLSForm contained a third tab. Is that the settings
tab? Could you tell us more about what project information you entered in that tab and how you entered it? If you're able to, it'd also be helpful if you could attach your XLSForm here.
Finally, when you get a chance, I'd encourage you to introduce yourself here. Doing so helps build community!