I just tried to access the freestuff>motorcycle which seemingly downloaded as a moto.rar file which is on my desktop. I am using a Mac 10.9.5 and Poser 10. Where does the folder need to be do that I can use it in Poser?

The moto.rar file need to be Un-compressed into your Poser 10 runtime.
If you don't know where your Poser runtime is, you should be able to find two folders named runtime in your Poser install if you search. For Ease of use, Please choose the one that is NOT in the Download folder. On a Windows Machine, the folder you want to unzip the Moto.rar file into is called Poser 10 Content.
Good Luck!

In order to open a .rar file, you will need Winrar - http://www.win-rar.com/start.html or 7-Zip - http://www.7-zip.org. Once the file is opened, you can unpack it directly into your /runtime directory or, even better, unpack it into it's own directory and then cut/paste it into your runtime directory.

You will find everything downloaded in a folder called downloads. Windows 10 will put everything downloaded in there and from the folder download you can take it in any folder you like. From there you can put it in poser or in a external runtime.

Just an FYI, that Win-zip can also open .rar files, so if you have that then you don't need to get Win-Rar too. But the default unzip utility that comes wityh Windows won't do it