how to perform post operation for only attendance property

Question

export interface EmpAttendence {
date: Date;
AttendanceValue: string;
}
import { EmpAttendence } from './attendance.model';
export interface Employee {
id: number;
Name: string;
Gender: string;
Email?: string;
phoneNumber?: number;
ContactPreference: string;
DateOfBirth: Date;
Department: string;
IsActive: boolean;
PhotoPath?: string;
present?: boolean;
leave?: boolean;
holiday?: boolean;
Attendance?: EmpAttendence[];
}

Above are model of my employee object.I have performed the get,post put and delete operations successfully.Now after performing post operation(i.e, after creating employees) i want to take their attendance by picking date from datepicker.Can someone help me how to insert values into the specific property(only attendance property) of existing employee. Forgive me if my question is wrong.I am struggling from lot of time.