If you get this error when trying to install:
Could not set include path. Please set it in your php.ini: include_path=.././include/Smarty/:.././include/tcpdf/:.././include/Pear/:./:.:../:/var/www/httpdocs/: ...etc
you have to do as follows: open php.ini file at your server and find include_path variable. Add string from error - .././include/Smarty/:.././include/tcpdf/:.././include/Pear/: - the : is separator here. When you are finished, save the file and run installation.
It should work normally now.
If you do not have permissions to change php.ini file, you have to ask your hosting provider to do this all for you...