> How on earth do you tune to Drop C which is CGCFAD?

Never done it, but...

6th string down a 3rd to C.
5th string down a whole step to G.
4th string down a whole step to C.
3rd string down a whole step to F.
2nd string down a whole step to A.
1st string down a whole step to D.

However, are you reading this from tab? Chances are, if it's a mainstream popular-type song, that you could play it in standard tuning or at least by only dropping the initial C on the 6th string. Lots of "guitarists" who play in bands that are popular are really not that talented when it comes to the mastery of their instrument. This results in a lot of songs being transcribed for tablature in alternate tunings when the alternate tuning isn't necessary. It just happens to change the key of the song or make one or two notes easier to reach. In the case of this alternate tuning, the purpose of dropping all of the strings one whole step is simply so that it will be in a different key, except for the 6th string C which would have been a 6th string D had the remainder of the strings been in proper tuning. My suggestion is this, because altering the tension of the strings on your guitar isn't great for the neck or strings and makes the feel of the guitar inconsistent and perhaps hard to adjust to: just play the song in Drop D tuning (6th string whole step down to D) and play the song a whole step higher than written. Or, if you can read music other than tablature, just ignore the tab and only tune down if you really need that low C.

Shan-Michael begins the transition-dar