Sorry - I just clicked through on autopilot, but where do these files go?
The zip files contain the registered assets, so you can place them wherever you want. Just unzip them to a folder of your choice.
It is usually preferable to use the 'User' folder of the logged in user.
For instance: I have a 'Construct2' folder off my 'User' path, and I have a folder called 'Assets'. I unzipped the file inside this 'Assets' folder.