Starting with version 1.0.1 Smuxi supports Tor using the SOCKS 5 proxy feature. Versions before 1.0.1 will not work with Tor, so check your version from the menu: Help -> About. Engine must say 1.0.1 or later.
First you need to install Tor on your computer where you have also Smuxi installed. You can obtain the Tor Browser which includes the Tor daemon for Windows and Linux from here.
On Debian and Ubuntu based systems it is just a matter of running this command:
sudo apt-get install tor
Now that Tor is installed and running you need to tell Smuxi that network connections should be done through Tor. This is very critical, else Smuxi will keep using your regular network connection.
Start Smuxi, go to Preferences -> Interface then under Advanced enable Show Advanced Settings. Now in Connection you will see Network Proxy, this is where Tor needs to be configured as shown:
Type: SOCKS 5 Host: 127.0.0.1 Port: 9150
If port 9150 does not work, the default port of the Tor daemon is 9050 and the default port of the Tor Browser is 9050. The Tor Browser has to be open and running.
Leave Username and Password empty, they are not needed.
After that confirm the changes using the OK button and restart Smuxi to take full effect of the changes.
After restarting Smuxi, a connection test should be done to make sure connections are really going through Tor. Simply connect to an pre-configured IRC network like OFTC and make a /whois lookup on your own nickname. If the connection went through Tor then it should look like this:
-!- meebey7 [~smuxi@5P6AABTWT.tor-irc.dnsbl.oftc.net] -!- realname: http://www.smuxi.org/ -!- channels: #smuxi -!- server: weber.oftc.net [Newark, NJ, USA] [338 (?) meebey7 255.255.255.255] actually using host -!- End of /WHOIS list.
The first line shows your nickname (meebey7), username (~smuxi) and your IP/host which should now be not your real IP but something with tor.
If you can't connect then either the Tor daemon is not running or the IRC network blocks Tor. Freenode for example requires a registered account for Tor users, and SASL support which Smuxi does not support yet.