The SSL VPN archive that is downloaded from the Smoothwall contains the Windows client. For other operating systems, different clients are needed. The SSL VPN running on Smoothwall is based on OpenVPN and connections will work from any OpenVPN client. Here is a list of possible clients to use for iOS, Android and Mac OS.
The client called Tunnelblick is our recommendation for OpenVPN on Mac OS. The client can be downloaded from https://tunnelblick.net.
The OpenVPN Connect client by OpenVPN Technologies is the official OpenVPN app which will work fine with the OpenVPN server on Smoothwall.
There are a good number of OpenVPN clients available for Android. The OpenVPN Client by colucci-web.it works fine (there is both a free and a paid version) and the official OpenVPN client by OpenVPN Technologies is also recommended.
For all these clients, extract the .ovpn file from the download archive and use that to import in the client software.
NOTE: If the external IP or host name of your Smoothwall changes, you should be able to edit the .ovpn file to reflect this, rather than generating a new archive. The .ovpn file is a text file.