To hire an employee in SAP SuccessFactors Employee Central, the assigned user (HR Rep) completes the Onboarding Pending Hires page in the Admin Center.

An Alerts icon appears in Manage Pending Hires if there are any issues in the hiring process (for example, if there is a missing value for a mandatory field). You can select the icon (triangle with exclamation point) to view the error message and continue to hire the user manually.
On the Admin Alerts page, in addition to Recruiting, Onboarding, and Onboarding 1.0 pending hire alerts, there are also Automatic Hire alerts (search for Errors in Automatic Hiring, grouped by candidate name.)

The HR Rep needs to add the new hire's Email, Phone, and Address Information.

The HR Rep also adds the Primary emergency contact information for the new hire and then clicks the Continue button.

On the last screen, the HR Rep clicks Submit at the bottom corner to add the new hire to Employee Central. At this point, the hire is now an employee.
Note
New Hires can automatically be hired into Employee Central by switching the feature on in Onboarding General Settings.