I can help with this. If you've entered an employee's pay information, don't worry, they can't be deleted. Only made inactive. Here's how you can make them active once again:
Go to the Payroll menu and go to the Employees tab.
Beside the name search box, choose Inactive Employees.
When you see the employee name there, go to the Status column.
From the list, choose Active.
To learn more about the processes on how to manage employees and other guides to help you with QuickBooks, see the following link: Edit or change employee info in payroll.
Let me know if you have any other questions on this! I'm here to help.