Note that skype is a 32bit binary and as such requires compat-32
ports tree to be enabled to work.

You enable compat-32 by.

mv /etc/ports/compat-32.rsync.inactive /etc/ports/compat-32.rsync

$EDITOR /etc/prt-get.conf

And add:

prtdir /usr/ports/compat-32

Also be sure to enable:

runscripts yes