Welcome to the Community space, JLWILL. I'm here to lend a hand.
If you're referring to getting an Employer ID Number (EIN), you'll need to contact IRS so they can assign your EIN or which is also called your Federal Tax Identification number.
Once you have it handy, to enter it in your QuickBooks Online (QBO) account, here's what you'll need to do:
Click the Gear icon at the top.
Select Account and settings.
In the left menu, click Company.
Go to the Company name section, and click the pencil icon.
In the EIN field, enter your EIN information.
Click Save, then Done.
But if you're referring to Taxpayer ID Number (TIN), I suggest contacting your state so they can issue it for you.