I found another solution that works for me and I wish to share with others that are planning to implement similar thing. First I have created folder "Files" in which I have placed .chm file. after that I have used Directory class to get current directory:
private void help_Click(object sender, EventArgs e)
{
path = Directory.GetCurrentDirectory();
//izmjeniti htm naziv file
System.Windows.Forms.Help.ShowHelp(this, "file://" + path + "\\Files\\Administration.chm", "DodavanjeKorisnika.htm");
}
After I have done this part, I have added chm file into Folder directory, and in VS I have click chm file, and choose: Build Action "Content" and Copy to Output Directory: "Copy always".
Basically this should work for everyone because, while deploying app with One Click Deploy, it will create/copy Folder structure with chm file, plus using method get current directory and concatenate it with that folder and file, you provide necessary path to this file...
Cheers :)