Notification to Employee as any employer of ther system hires the employee

I have designed a system in which the employees can set up their profile in the app those seeking for job opportunities and the employer can visit the users profile and hire the employee by clicking on the hire button on the user's profile. When the button is clicked, a dialog should appear for the employer to enter their details and send to employee. This should be notified to the employee as they login through a means of notification as which employee wants to hire them. There are two tables one for employee details and one for employer and the database is in sqlite. Now i want some help to built this notification system. I am confused for which method to use and how?? Thank you..