1. /opt/bin should be in the path. You can append this to your path by editing the ~/.profile file. Mine looks like this:
# Your previous /Users/bparanj/.profile file was backed up as /Users/bparanj/.profile.macports-saved_2010-06-07_at_22:52:52
# MacPorts Installer addition on 2010-06-07_at_22:52:52: adding an appropriate PATH variable for use with MacPorts.
# Finished adapting your PATH environment variable for use with MacPorts.
2. curl -OL http://downloads.sourceforge.net/project/levent/libevent/libevent-2.0/libevent-2.0.19-stable.tar.gz
3. tar xzf libevent-2.0.19-stable.tar.gz
4. cd libevent-2.0.19-stable
5. ./configure --prefix=/opt
7. sudo make install
8. tar xzf tmux-1.6
9. cd tmux-1.6
10. LDFLAGS="-L/opt/lib" CPPFLAGS="-I/opt/include" LIBS="-lresolv" ./configure --prefix=/opt
11. make && sudo make install
12 which tmux
showed that the older 1.4 version was being picked up from /opt/local/bin, I deleted it by : sudo rm /opt/local/bin/tmux