gistfile1.txt

procedure TForm1.SessionClick(Sender: TObject);
var
  JObj: TJSONObject;
  sToken: String;
begin
  RESTRequest1.ResetToDefaults;
  RESTClient1.ResetToDefaults;
  RESTResponse1.ResetToDefaults;

  RESTClient1.BaseURL := 'http://dreamfactory.app/api/v2';
  RESTRequest1.Resource := 'user/session';
  RESTRequest1.Accept := 'application/json';
  RESTRequest1.Method := TRESTRequestMethod.rmPOST;

  JObj := TJSONObject.Create;
  JObj.AddPair(TJSONPair.Create('email', email.Text));
  JObj.AddPair(TJSONPair.Create('password', password.Text));
  RESTRequest1.AddBody(JObj);
  RESTRequest1.Accept := 'application/json';
  try
    RESTRequest1.Execute;
  except
    On E: Exception do
....
  end;

  JObj.Free;

  if RESTRequest1.Response.GetSimpleValue('session_token', sToken) then
  begin
    session.Text := sToken;
  end;