How can I go back and let employees fill out their own withholdings once I put some of the information in?

I can help you with adding your employee's information, @creativeedgecabi.

You can invite them to QuickBooks Workforce with an email link by setting up some information and then letting them add the rest of their information. 

Here's how to set up and invite a new employee:

1. Go to the Payroll menu and then Employees.
2. Click on Add an employee.
3. Provide your employee's info including their email address. This will automatically invite your employee to see their pay stubs and W-2s. They'll get an email with instructions to set up their Workforce account.
4. Select Done.

From here, your employee will receive an email with a link to set up and use QuickBooks Workforce to add their personal info and view their pay stubs and W-2s.

You can also make changes to an employee who is already in the account. You can update an employee from their profile or while you run payroll. See this article for detailed guidance: Edit or change employee info in payroll. 

In case you need to update employee statuses, check this reference for more information: Terminate or change your employee's status on payroll.

I'm always here if you need further guidance in updating your employee's information. Take care and have a great rest of the day!