Go to King & Dundurn (or Main & Dundurn...whichever road goes TOWARD Mac). There's a Go Bus that takes you to the train station from there (it'll say Aldershot IIRC). Take the train, wait an eternity, you'll reach Port Credit.
Take the 34 (don't take my word for it, look it up) and you'll be back to Sq. One
(pun intended)
the whole journey will take $3 (from Mac to Go station), $3 from Port Credit to Sq One, and the Go ticket itself.