StringParse function is a part of Functions4U package, which should have been automatically installed if you already installed SysInfo package, using UppHub.
What you should do to use SysInfo package:
1) Add the SysInfo package to your project (using TheIDE)
2) Include SysInfo header in your h or cpp file:
#include <SysInfo/SysInfo.h>
3) Don't forget to add
using namespace Upp;
to your cpp file OR call your functions with Upp:: namespace, e.g.