BOOL openDBFfile(char* filename);

This function opens DBF file. It accepts a string and returns a boolean value, true if everything was good.
Do not forget to close your file if you do not need it anymore.

{
    cdbfapiPlus* dbf = new cdbfapiPlus();
    if (!dbf) return;
    
    if (dbf->openDBFfile("c:\\tmp\\example.dbf"))
    {
        // your code
        dbf->closeDBFFile();
    }
    delete(dbf);
}