How do I access the files on my PC?

I may be being very stupid, because I want to transfer files from my PC to my android device, and I can't see any way to access my PC's files. When I launch the AirDroid site on my PC, it asks for the code from my tablet, which I enter successfully. It then shows what is on my tablet. How do I access the files on my PC to upload them to the tablet?

I have worked out how to do it. A case of RTFM. Sorry

Enjoy