how to add SSL to login authentication code?

string[] credentials = Encoding.ASCII.GetString(Convert.FromBase64String(authValue.Parameter)).Split(new[] { ':' });
            if (credentials.Length != 2 || string.IsNullOrEmpty(credentials[0]) || string.IsNullOrEmpty(credentials[1]))
            {
                //return Unauthorized(request);
                var resp = new HttpResponseMessage(HttpStatusCode.NotFound)
                {
                    Content = new StringContent(string.Format("access denied")),
                };
            }
            ClaimRole user = repository.trial(credentials[0], credentials[1]);
            ClaimRole user2 = repository.unlim(credentials[0], credentials[1]);
                if (user == null || user2 == null )
                {
                var resp = new HttpResponseMessage(HttpStatusCode.NotFound)
                {
                    Content = new StringContent(string.Format("access denied")),
                };
            }
            else
            {
               IPrincipal principal = new GenericPrincipal(new GenericIdentity(user.Username, BasicAuthResponseHeaderValue), new string[] { user.role });
                //IPrincipal principal = new GenericPrincipal(new GenericIdentity(user.Username, BasicAuthResponseHeaderValue), null);
                Thread.CurrentPrincipal = principal;
                HttpContext.Current.User = principal;
            }

            return base.SendAsync(request, cancellationToken);
        }