If you are stored in the system as an employee, you have the authorization to apply for shifts by default.
If you are logged in as Admin, you can view the applications of employees as follows:
In the calendar view with a blue dot next to the respective shift.
Within a shift with a blue dot next to the employee.
The blue dot shows you which "available applications" there are for which shifts.
IMPORTANT: As soon as an employee is assigned to shifts that overlap, this application is no longer "available".
The reference to the shift, which the employee applied for, still stays the same.
You can have the reference displayed to you by using the quick-add mode in the calendar (click on the employee name). All the shifts referenced to the employee are shown here. Accordingly, so are the shifts that the employee applied for, but the application is no longer "available" because of a different allocation.