Do you actually mean SSH (Secure Socket Shell) or are you talking about SSL (Secured Sockets Layer)..
My guess would be SSL as SSH is used for connecting to shells as the name suggests, and if you are talking about SSL, mIRC already supports it but is
ONLY accessible and visible in the options (alt+o) when the correct files are installed (namely, the
OpenSSL files).
If they are you can connect to a SSL server using the alt+o options or by prefixing the PORT with a + sign in the /server command or using the /server -e switch.
Eamonn.