Many-to-many relationship between own model and SimpleMembership user MVC 4

Question

I am using the MVC4, as well as the EntityFramework and the SimpleMembershipProvider. I have two DBs, one created with the simplemembership and the other is MyProjectContext. I have a model enrollment:

public class Enrollment
    {
        public virtual int EnrollmentId { get; set; }
        public virtual string Name { get; set; }
        public virtual List<UserProfile> Users { get; set; }     
    }

And in the UserProfile:

 public class UserProfile
    {
        [Key]
        [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
        public int UserId { get; set; }
        public string UserName { get; set; }

        public List<Enrollment> Enrollments { get; set; }
    }

And to create the many-to-many relationship:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Enrollment>()
                .HasMany(u => u.Users)
                .WithMany(r => r.Enrollments)
                .Map(m =>
                {
                    m.ToTable("User_Enrollment");
                    m.MapLeftKey("EnrollmentId");
                    m.MapRightKey("UserId");
                });
        }

but when i run it, it creates a table UserProfile in my DB without any users. I want to create a relationship with the table that contains the users and my model. How can i do it? Thanks