Encrypt Existing SQL Server Values Using MVC 4 Default Password Encryption

I created a new MVC 4 project and modified the connectionString slightly to point to a different db table. When I Register a new user the code below uses my existing UserTable and appears to creates 4 additional tables, the UserTable and webpages_Membership table are the ones I am interested in.

//InitializeSimpleMembershipAttribute.cs      
        private class SimpleMembershipInitializer
        {
            public SimpleMembershipInitializer()
            {
                Database.SetInitializer<UsersContext>(null);

                try
                {
                    using (var context = new UsersContext())
                    {
                        if (!context.Database.Exists())
                        {
                            // Create the SimpleMembership database without Entity Framework migration schema
                            ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
                        }
                    }

                    WebSecurity.InitializeDatabaseConnection("DBConnectionString", "UserTable", "UserID", "UserName", autoCreateTables: true);
                }
                catch (Exception ex)
                {
                    throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized. For more information, please see http://go.microsoft.com/fwlink/?LinkId=256588", ex);
                }
            }
        }

My UserTable contains 3 fields, UserID, UserName, and Password. The webpages_Membership table contains UserID, Password, it also contains other fields that I am not worried about at the moment. When I Register the new user the UserID and UserName are stored in the UserTable (Password is left blank in this table). The password is encrypted and stored in the webpages_Membership table. I went into SQL server and created some new users with UserIDs, UserNames, and Passwords(not encrypted in this table) My question is how can I use the existing MVC4 password encryption to take the un-encrypted Password from the UserTable, encrypt it and place it into the webpages_Membership table. Then I will be able to run my project and Log In using a profile that was created directly in SQL Server.