To view Performance forms held against an employee, you can view these through their employee card. Navigate to;
People -> Employees
Select your employee from the dropdown and you'll be taken to the employee card:
If you scroll down a little further you'll find the Development section which can be expanded by clicking on it:
Clicking the Reviews button will take you to this page:
The employee reviews page shows all of the review forms for that employee, from here you can view the forms by clicking the Actions button followed by View.