I was looking to add instruments to CSC, and eventually found an old post directing another user to Patch Arena (here, this is the cakewalk section)

But my question is, they don't have any CSC or MC6 folders, so can I still download them (the Museum collection in particular) from a different program and use it with MC6? Also if I can, where exactly would I put it?

You guys have been extremely helpful so far, and I'm hoping I can get an answer back on this :D.

-E-

I'm always a bit wary of "free" sites when the sounds and other things are for sale on cake's site. 

could be cracked or virus infected.  I tend to avoid them now all the time. 

I would buy the sound packs from cake before downloading something from an unknown site for free.  Keep an eye on the cake store and in the software forum here. Others will often alert you to free stuff from cake and really reduced prices from time to time. 

I have picked up some great deals this way. 

Patch Arena is legit. Those patches are from longtime Cakewalk users.
However, they will not work in Sound Center. They are specific to the synths for which they are intended. The Sound Center patches are borrowed from Rapture, DimPro, and z3ta, but they have been reformatted.
The Mus3um collections are very cool, but you do need to have Rapture or Rapture LE to use them. Rapture itself will work in MC. It is $99 for the download, and well worth it if you are interested in that sort of synth.
I do totally agree with Guitarhacker, as there are many sites offering obvious cracked software, and these are an invitation for trouble.

+1 to Bob.  

CSC does not support free sounds, it,s proprietary to cakewalk.  but there are some free legit sites available.  mostly either sfz or maybe some free kontakt sounds.  most of the free kontakt sounds also require full kontakt to play the , but some will play in the free player.