MVC6 Access DbContext From Classes Not Related To Controller

I am developing a ASP.Net5 MVC6 website Using EF7.

I wanted to access DbContext from one of my classes which is not being called from Controller.

Is it possible to access from there? If yes then please guide me a little so that I can learn how to do it.

So far searched a lot from GitHub and stackoverflow. Very little information on this topic.

If i need to inject to my class then how should I do it?

    public class CarAppContext : DbContext
{
    public DbSet<Car> Cars { get; set; }
    public DbSet<BodyType> BodyTypes { get; set; }
}

public Class NotificationManager
{
    CarAppContext ctx;
    public NotificationManager(CarAppContext AppCtx)
    {
        ctx = AppCtx;
    }
    public void SendNotification(Car HisCar, UserNotification HisNotification)
    {
        //need to check he has subscribed or not
        //ctx is null here
    }
}