How to Incorporate ASP.NET User Data in MVC Models

Hi Experts.  I'm just learning MVC5 and am having some trouble finding an example that shows me how I would model my data so that a table in which the ID of the creator of a record must be recorded.  The AspNetUsers table that is automatically created the first time a user registers on my site contains an Id field (nvarchar(128)) and my Company model includes a "CreatedBy" field which should have a one-to-many relationship with the AspNetUsers table.  Ultimately, users should only be able to view and interact with records related to the companies they have created (or to which the creator has given them permissions).  If I was doing a Database First project I would just create the relationship between the entities and Visual Studio would do the rest.  But this is a Code First project and I don't know how to make it happen.  Can you help?  Please let me know if you need additional information of clarification (I'm still learning the terminology so forgive me if I've gotten some of it wrong).  Thanks!

Company.cs (Model)

    public class Company
    {
        [Key]
        [Required]
        [ScaffoldColumn(false)]
        public int CompanyId { get; set; }

        [Required]
        [DataType(DataType.Text)]
        [StringLength(50, ErrorMessage = "Company name may not be more than 50 characters long.")]
        [MinLength(3)]
        [Display(Name = "Company Name")]
        public string CompanyName { get; set; }


        [Required]
        [DataType(DataType.Text)]
        [ScaffoldColumn(false)]
        public string CreatedBy { get; set; }

        [Required]
        [DataType(DataType.DateTime)]
        [ScaffoldColumn(false)]
        public System.DateTime Created { get; set; }

        public virtual ICollection<Item> Items { get; set; }

        public virtual ICollection<Category> Categories { get; set; }
    }

Select allOpen in new window

DatabaseInitializer.cs

        private static List<Company> GetCompanies()
        {
            var companies = new List<Company> {
                new Company {
                    CompanyId = 1,
                    CompanyName = "MyCompanyName",
                    CreatedBy = [Current USERID from AspNetUsers],
                    Created = System.DateTime.Now
                },
            };

            return companies;
        }

Select allOpen in new window