IExplorer is a desktop application allowing you to browse system files on your Apple devices like iPad and iPhone. You need to first install IExplorer and iTunes on your computer before you could see system files.
Once open iExplorer and connecting your your iPad / iPhone, you may see that System Library is not available. The reason you cannot see /System Library is because your device is not Jailbreak.
However, you are still be able to access the System Library in the backup section, as these are not locked. You could use Cydia to jailbreak your device if you must access the system files to make the changes.